Cliff Mass Weather Blog

Destruction Hits Two Sacred Weather Locations

2012-01-30T03:05:00.000-08:00

I was worried last week that when I revealed the secrets of the Devil's Weather Triangle near Napavine that some of the weather deities would be displeased. Such are the risks I take for this blog. Unfortunately, my fears were realized and two of the most sacred weather sites of the Northwest have been struck and damaged by sudden and unexpected severe weather. Not strong enough to destroy them, but enough to deliver a message. This can not be consider a coincidence.

My Napavine Triangle blog went out late Tuesday, and by Thursday morning a terrible fate struck my favorite weather-themed seafood restaurant: Ivar's Mukilteo landing. A strong westerly wind surge

pushed down the Strait of Juan de Fuca early Thursday morning, and the combination of large wind-driven waves and high tide resulted in strong wave action pushing under the restaurant. The water shoved the floor of the bar up by 8 inches and water surged upward through the unlatched hatch in the floor (see image). A geyser hit the ceiling, inundating Ivar's pride with brine and blowing out a window. This happened around 5 AM in the morning, according Bob Donegan, CEO of Ivar's. Fortunately, a maintenance worker was in the restaurant at the time, and at considerable personal peril, closed and locked the hatch during a lull in the waves. He deserves a years worth of chowder. A KOMO-TV story and video can be accessed by clicking on the image.

Using considerable resources, Ivar's brought in a large team to repair and dry the restaurant and on Friday it reopened, to the relief of many. As an aside, the ferry Cathlamet came in to the dock around 5:55 AM and the captain (Torger Skolman--I AM NOT MAKING UP THIS NAME) had to run the engines at half speed ahead in the dock to keep the ship form heaving in the slip and popping the auto apron off the car deck. A piling contractor in Everett Harbor measured gusts to 47 mph.

As many of you know, this restaurant was destroyed in another (and stronger) westerly wind surge through the Strait in October 2003. For this week's event, we started with relatively high tides (see tide table below), with the peak around 7 AM.

On Thursday morning, a low pressure system moved eastward over southern B.C., resulting in a large pressure difference building down the Strait (rising to about 6 hPa between Quillayute and Bellingham by 3 AM, and nearly as high at 4 AM). Air accelerated down the Strait, producing strong westerly winds over this gap and immediately downstream (see wind plot at 4 AM below). So with strong

winds building the waves, relatively high tides, and northwesterly winds pushing water towards the restaurant, Ivar's Mukilteo Landing restaurant was in Neptune's crosshairs.

But I was still worried. Was the sacrifice of Ivar's enough to placate the anger of the weather gods? Would they take on my most cherished weather site, the Langley Hill radar? The answer came quickly.

The Langley Hill Radar: Exposed and vulnerable

On Saturday morning, the radar showed a line of intense precipitation approaching the coast (see image at 2:35 AM, 9:53 UTC). Reds indicate very intense precipitation; such precipitation rates are often associated with thunderstorms.

Sure enough the U.S. lightning observation network (which can determine the location of lightning strikes by the electromagnetic radiation being emitted by them) indicated a line of lightning strikes associated with the strong radar echos (see below, for half hour ending 2:30 AM)

As the band of high precipitation and lightning passed over the Langley Hill site, the radar ceased to function, and was taken out of service for several hours until National Weather Service personnel could restore its function. A taste for the intensity of the lightning could be sampled by this wonderful image from Greg Johnson's webcam near Hansville (see below) at 1:36 AM.

I suspect there is only one way to stop the meteorological carnage: we must place some sort of sacrificial offering at the top of the Langley Hill tower. But what? Or whom?

3 PM Monday Update: KING-5 Jim Forman is now leading the polls for the great honor of appeasing the weather gods. With the parka, of course!

Weather Blogs Must Be Stopped!

An Unusual Winter Around the Country

2012-01-28T15:52:00.000-08:00

The weather is rarely normal and most years there are some large excursions from average conditions, but this year is rapidly becoming memorable over the eastern two-thirds of the country and Alaska.

In much of eastern U.S., winter hasn't really taken hold, with record maximum temperatures occurring on many days, and monthly averages being way above normal. Here are the anomalies (difference from normal) of the daily-average temperatures across the U.S. for the past 90 and 30 days (see below). For the last 90 days nearly all locations over and east of the Rockies has been much warmer than normal..with some places of the the northern plains as much as 8F above typical temperatures. That is really large. Guess who has been cooler than normal? The western side of the Pacific Northwest. We can't win! Cooler than normal temperatures have extended down to coastal CA and the far southwest, chilling those poor golfers and retirees in Palm Springs and Tucson.

The last 30 days has shown the same pattern,except that the warmth over the upper plains and Rockies have became even more accentuated.

To illustrate, here are the high temperatures across the U.S. yesterday. 60s in NY and New Jersey and 30s into the northern plains.

While most of the continental U.S. is mild and comfortable, western Alaska is having one of their coldest years on record. My colleague Mark Albright (past WA state climatologist) noted that Fairbanks during January 2012 is on track to be the coldest January in the past 40 years. King Salmon at the head of Bristol Bay is running -24 degrees F below normal for the month so far with an average temperature of -8 F. The coldest January on record averaged -3 F in 1956 at King Salmon where records go back 68 years to 1955.

80 miles west of Fairbanks at the confluence of the Tanana and Yukon Rivers lies the town of Tanana. After a low of -58 F yesterday followed by a high of -47 F, today is even colder with the latest reading of -60F this morning. Even more amazing, the Jim River site (180 miles N of Fairbanks) near Prospect Creek reported -77 F this morning. Prospect Creek holds the record for coldest place in the United States at -80 F on 23 January 1971. Yes, they were within 3F of the COLDEST TEMPERATURE EVER OBSERVED OVER THE U.S.

Now what is the cause of this? A very disturbed atmospheric flow configuration. Here are the anomalies...differences from normal... of the heights of the 500 hPA pressure surface (about midway up in the atmosphere). Ridging (higher than normal heights) over much of the U.S. and an anomalous deep trough over Alaska and western Canada. A very persistent pattern.

According to the National Weather Service's Climate Prediction Center this usual situation is not over yet. Here are the predictions for the next 6-10 days. MUCH warmer than normal conditions over the much of the U.S. (even us) as well as being considerably drier than normal. Cooler than normal over Alaska and southern Florida.

The reason...the U.S. ensemble systems are going for a BIG ridge over the western U.S. Here is the prediction for Friday at 4 PM for 500 hPa heights. The European Center forecasts (the gold standard) show the same thing...after Thursday the weather over the western U.S. goes dead.

We have a few wet weather systems to get through before then...starting tomorrow morning... but no lowland snow or major storms. We now have only a month left of western WA winter---after the 3rd week of February the worst is almost always over the lowlands. The sun becomes stronger, bulbs push up, and the lawns need to be mowed again. And yes, we can start thinking about those tomato plants.

The Truth About the Pacific "Data Void"

2012-01-26T21:29:00.000-08:00

How often do you hear statements like this?

Forecasting skill is bad on the West Coast because there are few weather observations over the Pacific.

We don't know what is coming from the west, so it is impossible to forecast in the Northwest.

In reality these statements are really not true. We have a huge amount of information over the Pacific and that is probably the main reason why weather forecasts have improved so much over the past 30 years.

So what observing assets do we have out there? Be ready to be impressed!

We start with weather buoys, as shown by this map (red diamonds indicate stations that have not reported during the past 8 hrs)

Buoys are good, but the problem is that they often are put out of commission with the first big storm. The big ones are anchored, and a bunch of them just drift around. Here is what one of the fixed buoys looks like (46005, roughly 330 miles west of Aberdeen, WA).

Then there weather observations from commercial ships. As part of the Volunteer Observing System (VOS), mariners take observations every six hours. The light blue dots on this chart show where ships were reporting at one particular time:

For some reason there are less ship reports in the middle of night. And as forecasts get better, the ships avoid the areas we really need data---in the middle and near major storms. When forecasts were bad, ships would get trapped in dangerous conditions--now they can get out of the way.

To forecast the atmosphere we need data aloft, since the atmosphere is completely 3D. A relatively new source of information (few decades) is from commercial planes. A number of wide-body aircraft provide important weather data (temperature and winds, mainly). Most of this information is at flight level (typically 30-40 thousand feet), but we also get nice vertical soundings when they land and take off. Here is an example for three-hours on January 7th of this year. Lots of data for flights going to Hawaii and to Asia. But there are holes...big ones.

Well, the sources shown above only represent a few percent of the observations we get. The bulk are from weather satellites. For example, some satellites can figure out the winds aloft by tracking clouds at various levels. Or they can sense variations in water vapor and track them. We get tens of thousands of wind reports per day in this way. Here is a small sample. Hundreds of wind reports!

But it gets better than that. You remember Star Trek when they orbited a new planet and Mr. Spock scanned the atmosphere and told Captain Kirk about the structure and composition of the atmosphere below? We can do that, perhaps even better than the folks on the U.S.S. Enterprise.


Getting ready to check the atmosphere of planet Beta-5.

Here is an example of a vertical sounding (temperature and humidity structure with height) at a location over the Pacific from a National Weather Service GOES satellite.

Satellites can do much more. By sending microwave radiation down to the ocean surface and measuring how much is scattered back, some satellite can tell us the wind speed and direction. Don't believe me? Check this out!

And there is MUCH, MUCH more. The bottom line is that meteorologists now have massive amounts of information from around the globe and this information is used to create a 3D initialization for numerical weather prediction models. We may have some holes and gaps at times, but we are no longer blind over the oceans and polar regions--there are huge amounts of data everywhere.

There is one figure that reveals the impact of all this data on forecasts so beautifully that I have to show you...check the figure below. This tells you about forecast skill in the northern and southern hemisphere from 1981 to now. It is about the skill at 500 hPA--around 18,000 ft, a good middle level. The higher the number (anomaly correlation) the better--100 would be a perfect forecast. You see the forecasts for various forecast ranges (3, 5, 7, and 10 days, varying color). For each color the top line in for the northern hemisphere and the bottom line for the southern hemisphere.

It is clear that forecast skill for both hemisphere has greatly improved over time.

But there is something even more profound. Back in the 80s, the northern hemisphere, with more land area and far more observations, had much higher skill. But that seemed to change in the 90s and the early part of this century. Why? The answer is the satellites. During that period major advances in using satellite data in weather prediction were made. Since there is about as much satellite data in the southern hemisphere as the northern, why should the northern hemisphere have better forecasts?

I was really stunned when I saw this figure for the first time. Few graphs illustrate so concisely how far we have come.

With more satellite data sets coming on line during the next decade, and improvements in the technology of data assimilation, expect further improvements in weather forecasts.

The Bermuda Triangle of Northwest Weather

2012-01-24T21:01:00.000-08:00

Some things are beyond scientific understanding. Weather phenomena that can not be explained by forecast models and high-tech observations. Occurrences that are known by local meteorologists but are rarely spoken about in public. Perhaps the best-known example: the Napavine Triangle.

Napavine is located in southwest Washington, between Olympia and Portland--a few miles south of Chehalis (see graphic). A closer look at the terrain reveals a triangular valley (second map). A valley with extreme and often bizarre weather.

The nearly perfect triangular shape of the valley is suggestive of supernatural influences.

Doubtful? You won't be in a few minutes. During the snows last week, which low-level (below 500 ft) location got more snow than any other in western Washington? Napavine with 25.5 inches. Here is a picture of what things looked like on the ground:


Picture courtesy of http://napavineweather.info/wordpress/

And where was the only place in western Washington to be hit by a tornado last year?
You guessed it. Napavine. Here is a small sample of the damage:

And in 2007 and 2009 what town, located next to a major river, experienced flooding that closed the nearby Interstate for days? Yes, you guessed it, Napavine.

And during the extreme heat wave of July 29, 2009 where was the warmest temperatures in western Washington? Locations rising to 110 or 114F. Yes, the Napavine triangle (see graphic located here for proof).

I could give you a long list of other examples of natural disasters in the scary Napavine triangle, but you get the message.

And did I tell you about the Bigfoot sightings/evidence in Napavine? Yes, it is true...here is the proof: http://bigfootevidence.blogspot.com/2011/09/recent-sighting-report-woman-finds.html

The motto of the town is "Welcome to Napavine, for a day or a lifetime." You better keep your eye on the sky (and the forest) if you want to do either.

But as long as I am talking about the bizarre, I just learned of a new weather threat here in the Northwest (kudos to Dr. Brad Smull). Burial by sand. I AM NOT KIDDING. Last week, there were sustained extremely strong winds along the Oregon coast, as a huge pressure gradient was maintained between high pressure over California and the low pressure systems moving eastward near the WA/OR border. Here are the sustained winds at Newport and North Bend, Oregon (as well as Sea Tac thrown in for comparison) for the past two weeks. One major wind event after another along the coast! Gust were much higher.

In some coastal towns large amounts of sand was blown by this strong winds, burying homes nearly completely. Consider what happened in Waldport (see map),

or what is left of it. Look at these amazing pictures by Jason Durrett:

A news video is found here. Here are a few others I found on the web:

Now those houses are basically gone! Perhaps they will be unburied in a future age, like the buried pyramids of Giza.

PS: A few of you have complained that I sometimes edit my blogs after I release them. Folks..this is my style. I write this blogs fast and then like to go back and perfect them, sometimes based on your comments. I don't want to have multiple blogs each day, except during big storms. Others complain that they don't like me talking about education during 1 in a few dozen blogs. This is my personal blog, please allow me to deal with it in my own way. There are many other weather blogs, they may be a better fit for some.

UW Admissions and Failing K-12 Education

2012-01-23T22:02:00.000-08:00

A week ago there was an article in the Seattle Times describing a large drop in applicants to the UW this year. Considering that other WA State schools have not seen a similar decline and all state colleges are experiencing essentially the same tuition increases, why are UW applications down?

Could it be the incessant articles and editorials by the Seattle Times about how the UW is turning down strong applicants to let in more out of state students? How about this Seattle Times headline last spring:

"Why straight-A's may not get you into the UW this year"

which suggested that
"High-school seniors with top test scores didn't get in.
Students who got into more prestigious schools were wait-listed at the UW.
Valedictorians with straight-A's were denied admission, while out-of-state students with lower grades were accepted."

The truth is that this story was essentially false--I knew this since I had a long talk with the UW Dean of Admissions about it, was well as being undergrad adviser in my department for over a decade.

The truth is that the UW does not reject strong students: those with a combination of good grades, high board scores, challenging classes, and good recommendations (honor applicants only). Straight A students with lower board scores, easy classes, or other negatives may be rejected, but that is to be expected at the State's flagship school and one of the top 20 universities in the world according to some evaluations. In a day of extreme grade inflation, an A average does not mean what it used to be. The average GPA of incoming UW freshman is A-.

I believe this kind of irresponsible journalism has harmed the UW unnecessarily.

(Parenthetical note: my mentioning the problems with this ST article on KUOW is what led to me being kicked off that station. Irony Alert: Kicked off of KUOW Weekday defending the UW on the UW radio station, because I was worried about damage to the UW that actually occurred)

Another thing the ST got wrong was the quality of the out-of-state students: they are generally HIGHER than in-state applicants. Better grades and board scores, for example. (Let me make it clear, many WA State students are very strong).

Now the controversial part of this blog! Is is REALLY a bad thing if we let in more out of state students?

Yes, they help pay the bills by helping support in-state students. In other words, the UW can admit more in-state students if more out-of-state students are admitted.

Let me be frank, there are quite a few UW students who don't belong here. Whose seats would be better filled with out-of-state students. It is distressing to admit, that a good number of UW freshmen (perhaps the lower 10-15%) do not have college-level skills.   They can't do basic algebra or middle school math (many can't even do long division or fractions). Their spelling and writing are atrocious--unable to write coherent sentences. Their student habits are deficient, including poor attendance and note taking. They have poor research skills and have difficulty working independently. Some have poor attitudes and clearly would rather be some place else.

Many of them have little hope of success at the UW and a significant number drop out, or shuffle their way through their college career with marginal grades and no direction. They leave the UW little better for the experience. For many, the problems are not of their making: their preparation in our state's K-12 system was so poor that they had little chance. And the problems of poor K-12 preparation is particularly acute in technological subjects that require strong math and science skills. Several times I have had a tearful undergraduate in my room, who desperately wanted to be a meteorologist, but had to give up their dream because their math preparation in K-12 was so poor that they could not make it up in a reasonable time.

So I ask, why not accept the creme-of-the-crop of out of state students to replace the lowest tier of UW applicants?   Many will develop a liking for our state and decide to stay here, thus enriching our state's employment pool.

Outrageous you say? Well folks, our country is doing just this in a major way. U.S. K-12 education is weak, particularly in math and science.   Ever check out the student demographics in engineering and technical subjects in our colleges and universities? Or the ranks of the faculty in technical areas? They are filled with the foreign born. Why? Our country is incapable of training enough technically skilled young people to keep our 21st century nation running, so we DEPEND on foreign imports. Without them our society would fall into 3rd world technological status.   When I go to meetings on meteorological data assimilation, probably the most mathematically intense subject in my field, I muse that they might as well have the presentations in Chinese, there are so few native Americans in the room.   Check the faculty of the UW Statistics department--how many were born in the U.S.? Not many. The problem is the the U.S. can't keep this approach going indefinitely: as China and India develop, their students will not want to come here anymore. And then we will be in real trouble! We need to be insure our own students get the best education and are capable of filling our needs for a technically trained work force.

What is happening to WA State and U.S. student is really a tragedy for them and our society. We need to turn around U.S. K-12 education, particularly in mathematics and science. And it is quite possible to do so, perhaps even spending less money than we do now. Groups like the Gates Foundation, League of Education Voters, and the Broad Foundation have good intentions but they are pushing ineffective, unproven and faddish approaches such as charter schools, Teach for America, micromanaging teachers, and fixation on assessments, and they don't base their approaches on empirically proven methodologies. They are part of the problem, not the solution.

In a future blog I provide some concrete suggestions of how we can improve our state's K-12 educational system. Some points I will make:

1. We need strong curricula that include all important material. Curricula must insure students have the skills and knowledge to succeed in college, if that is what they want to do.
2. We need to reduce use of obscenely expensive textbooks and materials.
3. We need to insure teachers know the subjects they teach and then get out of their way.
4. We need to spend less on assessments.
5. We need not waste 300 million dollars on new, unproven Common Core Standards.
6. Colleges of education are generally failing institutions that need to be restructured with more training on subject matter and how to teach effectively, and less social engineering.
7. Decisions on curricula and teaching approaches must be based on robust research using modern statistical techniques, something nearly absent in the U.S. educational community.

...and more.

Southeast Olympic Snowstorm

2012-01-22T13:23:00.000-08:00

It is snowing right now at fairly low elevations to the southeast of the Olympics--something that happens a few times every winter. For example, here is an image from Dale Ireland's home above Hood Canal

At the same time it is raining and in the upper 30s and lower 40s in much of the rest of the area. How can this be? The National Weather Service has been spotlighting this possibility for a while and the local high resolution models were going for this snow for days (see forecast from yesterday below-24h snowfall ending 4 PM) for forecast initialized 4 PM yesterday.

The key to this is southeasterly flow and the cooling influence of melting. A strong low is approaching the coast (see graphic) and that has forced strong southeasterly flow over

western Washington. To prove this, here are the profiler winds above Seattle for the past day (see graphic). Strong SE flow through depth (latest observations on the left).

When strong flow approaches the Olympics it is forced to rise, producing enhanced precipitation rates. To see this, here is the latest Camano Island radar image (it can't see southern side of the Olympics well, but you get the idea). You can see the impact of the Olympics, with heavier precip on the eastern side of the barrier.

Our precipitation aloft in winter is nearly always in the form of snow, as the snow falls into an initially warmer layer below (a layer above freezing) melting occurs. Melting causes cooling. That allows the snow level to move downward and potentially to the surface.

So southeasterly flow causes upslope on the mountains, which causes a heavier precipitation rate, which causes more melting and cooling, which results in the snow level coming down to the surface. This effect can also happen in other areas of enhanced precipitation, such as the Puget Sound convergence zone.

You pull the tail of a tiger and it is going to snap at you! On Tuesday, my blog noted that a ST writer was making fun of forecasters for changing their predictions in time. And on Wednesday, I complained about the big headline of MEGASTORM in the ST that day, when the latest forecasts were only for 3-6 inches over Seattle.

Well, the ST began with reporter Nick Provenza in an article "Forecasts Change, Right? Professor Mass" in which he pointed at my earlier speculation that a heavy snow was possible (my forecast subsequently changed with new model output). Sort of like suggesting that I was the meteorological version of Newt Gingrich, calling for moral purity while he was playing around with multiple women. But I only gave one forecast at a time! Monographical prediction.

And today they brought out the heavy artillery: ST humorist Ron Judd, who suggested an "about-face forecasting retreat on Tuesday." As if holding to a failing forecast is the route to victory!

Now a bit of good-natured ribbing is fine, but this correspondence shows that many, including some ST folks, don't appreciate the essential nature of forecasting, and particularly that forecasts change in time, and generally improve as you get closer. My profession needs to find a way to communicate the evolving forecast without losing the confidence of the media and the public. Polls change in time and people don't seem to get upset and make fun of pollsters. We need the same for meteorologists!

By the way, there is a pretty good story today in the ST on the ice-storm forecast by reporters who took the time to understand the problem.

Finally, a fun parody of the local snowstorm coverage is now available:

http://www.youtube.com/watch?v=hHqcf0jcPRk

The Other Snow Story

2012-01-21T09:13:00.000-08:00

During the past several days, this blog was been fixated on lowland snow and ice. Later I would like to talk more about the ice storm, which has been one of the major meteorological disasters of the past decade, with roughly 300,000 customer losing power, massive loss of trees, extensive road closures, and loss of life.

But another important weather story has been the huge increase in snowpack during the past week over the Cascades. Below is the NOAA snowdepth graphics comparing January 13th to today. Big increases. Enough to make ski operators and outdoor enthusiasts smile.

Before

After

A week ago, the Oregon snowpack (snow water equivalent, the amount of water when melted in the snowpack) was only around 35% and the Washington snowpack had dropped to below normal (70-90%). Below is the situation yesterday (click on image to enlarge). 85-100% for Washington and now 50% in southern Oregon to around 80% in the north. Big improvement.

In contrast, there is a real serious snow drought in California, with stations in the Sierra's at 10-15%. 6-12 inches new around Tahoe today....they need it. Utah and Colorado are also well below normal. Folks in those states like to smirk and criticize our snow. Not this year.

The Cascade passes have received a lot of snow (3-4 feet) during the past week, roughly doubling their snow depth. Here are the Snoqualmie totals: 43 to 80 inches!

And here are the snow depth graphs for Ollalie Meadows (near Snoqualmie) and Stevens Pass. Major jumps in snow the past week.

Ollalie Meadows

Stevens

According to the latest model runs, the increase in show should continue, but at a lesser rate. Here are the snowfall predictions for the 24h periods ending Sunday and Monday at 4 AM. 6-18 inches of snow. And good news for CA: more snow for the Sierra's. And yes, those smug folks in Utah will get quite a bit.

One final thing.

With all this snow the avalanche danger in the Cascades is quite high. First we had an extended period of relatively cool conditions and little snow. That resulted in the formation of a surface crust.   Then starting about a week ago we had a lot of snow under cool conditions. That produces low-density, fluffy snow. Perfect for skiing...Cascade powder! (Utah snow boosters take note!).

Over the past few days temperatures aloft warmed and there was lots of wetter, denser snow. So we have dense snow, over light snow, over a crust that acts as a ball-bearing for the upper layers to slide off of. That implies serious avalanche danger, and my colleagues at the Northwest Avalanche Center and the National Weather Service have warnings out. Back country skiing might not be a great idea today, and I would not be surprised if there is some avalanche work for some state highways.

Lost Dog Report

We have a few sightings the last week up in Mountlake Terrace...and we rushed up there immediately, but no luck. We then staged some food and attractive scents (chicken broth) and put a infrared controlled digital camera there to snap pictures of what came. Lots of business: local cats and a white/gray dog. An animal psychic told us that she connected our dog with a white van and a guy in his 40s.

A major problem with us is that some individuals (or others) are tearing down our signs (ALL OF WHICH ARE ON PRIVATE PROPERTY). Some kind people allowed us to put a sign on their property (48th Ave next to the Mormon Church).   Now it is gone. Maddening.

The End (Of Lowland Snow, Cold and Ice) is Near

2012-01-19T22:38:00.000-08:00

This snow/sleet/freezing rain evident is basically done. And we are not talking about forecasts...observations show its demise.

First, only a handful of observing sites in the south Sound are indicating a few light snow or freezing drizzle showers...this will end soon

The radar shows NOTHING offshore:

But most important of all, the profiler at Sand Point in Seattle shows southerly winds and warmer temperatures rapidly descending towards the surface, at this rate we should see the end of the cool northerly flow over the Sound and a replacement by warming southerlies by daybreak (latest observations on the left side). I have indicated the northerlies and southerlies on the figures. Temps in red.

Finally, a neighbor of mine, Wally Powelson, who is an Alaska Airlines jet captain, shared a few pictures from Sea-Tac showing the substantial icing on the planes...no wonder many flights were cancelled. How often do you see icicles on planes? This was a historic freezing rain event, the most significant since December 1996.

Now I hate to bring this up.... but the forecast models for the next week indicate some intense weather in store for us. Heavy rains, strong windstorms, and the arrival of frigid arctic air. Jim Cantore from the Weather Channel may have to come back for another visit.

Major Freezing Rain/Snow Event

2012-01-19T11:58:00.000-08:00

I drove to the UW this morning. A big mistake, with a slush, packed ice, and snow along the way. In north Seattle the freezing rain left a 1/4 inch crust on the snow...and now it is turning into snow as the precipitation intensity increases. (I understand the city is now sending out plows to take care of these roads)

Icy Window at Sea Tac: Picture Courtesy of Seattle PI

Well folks, this is not my profession's finest hour. We had forecast the continuation of the light freezing drizzle of yesterday (an irritant, but not a major threat) and then a warm-up today with rain coming in late. Our models did not indicate that the precipitation would move so far north, so fast.

One thing I think is clear...thank god for the new coastal radar. By 4:30 AM it showed that the forecast was going bad and moisture was streaming in farther north. (below is the Langely radar at 5 AM)
My colleagues in the NWS clearly understood the threat and put out an ice storm warming around 5:30 AM.

With precipitation streaming northward and cold air in place we have mixture of snow over the north Sound transitioning to sleet in the central Sound and freezing rain in the south. There are reports of 1/2 inch to one inch of freezing rain in the south and southeast Sound area (e.g., Olympia, Puyallup), with many downed trees and extensive power outages (over 100,000 customers reported by Puget Sound Energy, Tacoma Power, City Light).

Here is a neat figure showing the winds and temperatures in time over Seattle (time increases to the left, height in meters). You can see the southwesterly/southerly winds aloft associated with warmer temps, a thin layer of southeasterly air below that, and cool northerly flow near the surface. You can also see the descent of the freezing level over time.

At noon the back edge of the precipitation area (image) is apparent offshore, but clearly we have several hours more of this moderate snow/sleet/freezing rain event.

By tomorrow morning the winds should shift to the south at low levels with warmer temps. The end.

Picture courtesy of Puget Sound Energy

Icy Seating at Sea Tac: Picture Courtesy of Seattle PI

Ice Storm: Freezing Rain and Sleet

2012-01-19T07:03:00.000-08:00

From a bit of weather overload, I decided to take a break from this blog for a while, but the interest and importance of what is happening now is bringing me back online (and UW classes are cancelled so I don't have to be in class for my real job).

Over the past day and particularly this morning, something relatively unusual and, quite frankly, dangerous is going on outside--a freezing rain/sleet storm--and let me talk about it a bit.

I was woken up this morning by the sound of sleet (ice pellets) banging on my window. Walking outside, there were ice pellets falling and the snow had a thin crust on it. Yesterday, after the main snow, there was light freezing drizzle (and for some very small ice pellets) over much of the area.

This is a highly unusual situation here in western Washington: outside of the famous ice storms of the western Columbia Gorge (also known as the silver thaw), western Washington does not get freezing rain very often. The last big event was over the southern Sound in December 1996, when Sea Tac airport closed. The airport is closed right now

Why is this happening?

Right now a warm front is to our south, with temperatures in the 50s in the Willamette Valley, while north of Olympia temperatures are below freezing:
.

Yesterday, after the main action was over, we were left with a saturated lower atmosphere in which there was supercooled clouds---water droplet clouds that were below freezing through their entire depth. Yes, believe it or not liquid water can exist below freezing (typically in clean air from 0 to roughly -15C). Some of this cloud water was converted into freezing rain. Usual for us to see that.

But there is another way to get freezing rain (and sleet too): when warm air pushes in above a sub-freezing air mass near the surface. And that is happening right now.

Here is the temperature variation above Seattle now from the profiler located at the National Weather Service office at Sand Point.

Cool air at the surface, but then a rapid warming (an inversion) above 400 meters (temps in C--really something called virtual temperature--subtract about 1 for air temperature. The warm air (and southwesterly winds) have moved in aloft--a typical warm frontal structure (see graphic):

The precipitation area is reaching roughly to Everett based on the weather radar (see radar below).

Over the northern part of the domain the southwesterly air is high enough so that it is below freezing, so there is snow (Everett is snowing). But farther south, we have above-freezing air aloft and rain. Rain that is falling into below-freezing air. Some of this rain is freezing on the way down into ice pellets or sleet (what woke me up), but a lot of it is staying liquid and hitting the ground as freezing rain...which freezes on contact with the cold surface. The current freezing rain is a mixture of the two icing mechanisms (freezing drizzle from shallow clouds and freezing rain from aloft)

Dangerous stuff, that freezing rain. Not good for driving. I just noticed my colleagues at the National Weather Service have an ice storm warning out. Of course, this freezing rain/drizzle is on top of roadways that melted yesterday and then refroze. And here is the weather icon the NWS used for our weather this morning. You see an icon like that and you worry.

Anyway, today there will be wintry mix--freezing rain, ice pellets/sleet, snow, rain until the air warms up enough aloft to turn it all to rain (probably by later this afternoon)

For those of you who like to geek out on cool technology, here is the correlation map from the dual pol capability of the Camano Island weather radar. The pink indicates relatively uniform conditions an farther (and higher) out that indicates snow. Closer in (lower) you see reds and yellow. That is indicating melting snow and a mixture of snow, melting snow, and rain.

NORTHWEST WEATHER WORKSHOP: The Pacific Northwest Weather Workshop, the main annual gathering for those interested in Northwest weather and climate, will be held on March 2-3, 2012 at the NOAA Sand Point facility in Seattle. For more information and to register please check the meeting web site: http://www.atmos.washington.edu/pnww/http://www.atmos.washington.edu/pnww/

Wednesday Morning: The End in Sight and Strong Oregon Winds

2012-01-18T10:02:00.000-08:00

The model's seem to be verifying well and amazingly the worst is almost over. In fact, it should really be all over for most of the western side of the Cascades by 1 PM. Here are the latest regional radar images (combining all local radars together) for 4, 6, 8, 10 and noon:

4AM

6AM

8AM

10AM

Noon

You will note that the back edge of the snow is moving in from the west and that even over the inland areas the intensity of declined substantially. The latest model runs indicate that snow will be mainly over by 1 PM and these radar images are consistent with this. Having the Langley Hill radar on the coast really gives us some confidence in the snow end times.

The forecasts seems quite solid...a few inches in the north sound, 2-4 inches around Seattle at low elevations, 6-10 inches around Olympia and south Sound, and MUCH more south of Olympia and north of Portland. Some extraordinary snowfalls around Napavine and nearby SW Washington areas--reports of 15-20 inches on the ground.

The warm front has moved northward up the Oregon Coast--warm and rain in Astoria and Portland. Long Beach (LONG2) was deluged with 1.6 inches of rain in just 5 hours between 4 AM and 9 AM as the warm front approached. During that time the temperature rose from 34 to 50 F. Now that's a warm front.

With the low moving towards the Oregon/WA border a huge pressure gradient has been created along the Oregon coast...with hurricane force winds from the south (see graphic).

Winds gusts to 99 mph at Point Blanco and above 60 mph at many locations.

And there is strong Fraser gap outflow winds moving in NW Washington (see graphic),

with true arctic air pushing to the SW. 12F in Bellingham with 20 kt winds! A lot of this flow is slamming into the Olympics, provide enhanced snowfall near Port Angeles and environs.

Once the precipitation is over this event is done...and tomorrow's system is going sufficiently south that precipitation will only reach to Olympia. Rain and warmer on Friday, washing the whole business away.

A Snowstorm of Two Characters

2012-01-17T21:27:00.000-08:00

The latest forecast models runs suggest a snow event of two characters. Over the mountains and over southwest Washington there will be large quantities of snow. And substantial snow over the eastern slopes of the Cascades. But over Puget Sound and northwest Washington this will be a very modest affair. In fact, many of you over the north Sound and Whidbey Island got WAY more snow today than you will get tomorrow.

Right now two signs of the incipient action are evident. First, the Langley Hill coastal radar is now showing the leading precipitation/clouds. You really have to love this radar!

And the 8 PM surface charts show true Arctic air moving into Bellingham. 14F temps at Bellingham Airport with a dewpoint of 10F. Cold air at Blaine and really frigid stuff (single digits and subzero) over southern BC. This air has not made much progress into Washington yet, but that will change as the low moves south of us.

Now to the important part. I have reviewed the latest National Weather Service forecast model output (4 PM), the forecasts from the UW high-res models, and the output from several ensemble prediction systems. The situation is similar to this morning, and IF ANYTHING DRIER WITH LESS SNOW OVER PUGET SOUND.

Here is the latest 24-h snowfall ending 4 PM tomorrow (the storm is over by then west of the Cascades) from the 4-km UW WRF model for both the region and western WA. Huge (like 3 feet+) snowfalls over the southern WA and Oregon Cascades. 8-15 inches over portions of SW Washington. 7-8 inches near Olympia, 2-4 inches over Seattle, 2 inches over Everett. Very little over Bellingham. Big snows over SE Washington.

I think this forecast is the best my discipline can give you for a single forecast. The latest update from the Seattle NWS office is consistent with the above numbers. Far better would be a probabilistic forecast: X% for 0-2 inches, Y% for 2-4 inches, Z% for 4-6 inches, etc. But that is for a latter blog. And yes, THERE is some uncertainty with this forecast--my gut feeling is there is perhaps a 20% chance it could go wrong in a serious way.

Finally, there is been a lot of talk about really strong winds tomorrow. My examination of the weather models suggest that the winds will only be strong (30 knots or more) over portions of NW Washington downstream of the Fraser River gap, the Strait, and offshore of Grays Harbor. The northerlies in the Sound will increase rapidly (to 20-30 mph over water) as the low center moves south of us, resulting in a large pressure difference between high pressure in southern BC and the low. Here are the predicted winds at 10 AM.

I wanted to end with an editorial comment. There were a number of folks that were concerned/upset about the fact that my and others forecasts have changed over the past few days (from slush to snow to lighter snow). One individual told me I needed to show more "character" and be strong enough to stay with my original forecast. An ill-informed (and somewhat insulting) writer for the Seattle Times wrote:

"How much snow could fall in the Seattle area Wednesday now appears to anybody's best guess." and then made fun of one of my colleagues at the National Weather Service.

The very nature of forecasts is that they tend to change in time. They become more accurate the closer you get in time to an event. A good forecaster will change the forecast as more information and new guidance becomes available. What would you have them do?

In one lecture of my senior weather forecasting class I talk about the psychology of weather forecasting and how they have to push previous forecasts out of their minds, not compensating for past errors. Forecasters need the mindset of one individual in particular:

Vulcans Make Excellent Weather Forecasters

Scaling Back

2012-01-17T08:50:00.000-08:00

UPDATE TONIGHT AT 9 PM. The 18 UTC model runs are consistent with the lesser snowfall totals of this morning's runs.

The latest series of model runs are in and to me they suggest we need to scale snow totals down over Puget Sound to 2-6 inches. In other words, not a record even over the PS area.. Folks this is a very difficult forecast. Everything depends on getting the track of the low exactly right...first to decide where the rain/snow changeover will be and secondly to get the amount of precipitation right.

Most of the models are in agreement that the low will go south of us...thus, more confidence that it will be pretty much all snow north of Olympia. But having the low go south is a Faustian bargain...it reduces the intensities over us. Right now it looks like 2-6 inches over Puget Sound (6 inches near Olympia, 2 inches near Everett) is the most consistent forecast with current model forecasts. Tonight will will have a better idea. As I mentioned before, a shift of a hundred miles or so for the low makes a huge difference on the forecast for us....a low that has developed over the past several days and over thousands of miles. It is amazing we can even attempt to do this.

Here is the latest 24-h snowfall totals ending 4 PM Wednesday. Big gradient of snow up the Sound but LOTS of snow over the mountains and SW Washington, before it turns to rain there.

If the predicted path or intensity of the incoming system changes, this forecast will change. It is sort of like aiming a rifle...you gyrate around until you lock on. The storm shifts 100 miles north...ST headline could be true.

Wednesday Snow Storm

2012-01-16T21:29:00.000-08:00

I just looked at the latest model runs and it seems clear that we are going to have a major (but not a record) snowstorm, one that is NOT followed by major warming and heavy rain. No Slushmageddon, just Snowmageddon. Near all modeling systems are taking the low south of us--thus the uncertainty is considerably less than a day or two ago. (But to be fair, there is a chance that the solutions we have are wrong!) With the low going south, the cold air can stay in place...in fact, the cold air will be reinforced with flow moving southward out of British Columbia. But a southward trajectory also lessens the precipitation amounts in the central and northern portions of the state...so NW WA may get very little.
Since the forecast is so critically dependent on the exact position of the low, we need to watch that today. There is still a chance this could end up as a wet event....snow turning to rain, particularly over the southwestern portion of WA.

And there is something else...ANOTHER pulse of snow will occur on Thursday.

Cutting to the chase, Seattle may well get 6+ inches of snow during the next two days. SW Washington could get more. The mountains, particularly the central Cascades southward could get feet--like 3-4 feet. In short, one of the biggest events we have had in years.

This has been a hard forecast for the models because there are two airstreams battling it out...one from the north and one from the south. Small displacements of the low (order of a few hundred miles) makes all the difference. Consider that the system has developed and moved over thousands of miles...this is not an easy thing to do.

There has been some hype about this event...it is NOT going to be as bad as December 1996. I remember that well. We had two snowstorm the last week in December and I had 21.5 inches on the ground at my house. Then it got very warm and windy and heavy rain rapidly melted the snow. Just a disaster, with collapsed roofs and slope failures.


Heavy snow followed by warm rain collapsed Edmonds boat shelters

You want to see some weather maps! You bet.

Tonight and tomorrow a weak disturbance is moving through with lots of snow showers. (see radar image below). Substantial snow shadowing in the lee (west) of the Olympics. Some folks out of the shadow will get a few (2-4) inches. Child's play compared to what will happen on Wednesday morning.

On Wednesday AM a low center, with an associated warm front will approach our region, and by 10 AM (42h forecast chart below) will be reaching the coast, while cool air remains in place over most of western WA. Another weaker low will follow on Thursday AM. Two snow events. Clearly, we are just on the edge of the interface between the cool and warm air, which makes the forecast much harder.

Here are the predicted snowfall maps for 24h ending 4 PM Tuesday (first one) and 4 PM Wednesday (second one). During the next 24h, there will be light snow over the western lowlands (less in the central Sound) and lots of snow in the mountains. For the subsequent 24 h, there are huge amounts in the Oregon and southern Washington Cascades and heavy amounts (8-12 inches) over the western lowlands. Eastern Washington and Oregon also get hit hard.

Here are blow up views for 24 hr snowfall ending 4 PM Tuesday, Wednesday, and Thursday

Bellingham gets cheated! And did I mention strong winds coming out of the Fraser River Valley and hitting NW Washington? Here is what is forecast for 1 PM on Wednesday:

Sometimes so much happens at once that is hard to keep up with it...Wednesday will be like that. This event will do wonders for the NW snowpack...particularly in Oregon where they have really been hurting. And we haven't talked about the extraordinary precipitation totals to the south of us, where some places will be getting 10-20 inches of rain (or its equivalent in snow) (see graphic):

As shown by this water vapor chart....this is the result of the famed pineapple express, with moisture streaming out of the tropics and subtropics towards the West Coast.

I am exhausted thinking about all this weather action. Anyway, lets watch this carefully tomorrow....looks solid...but no forecast is certain and if this prediction goes south, it won't be the first time. The southern part of the Washington could see snow turning to rain. Keep in mind EVERYTHNG is dependent on the location of the low pressure...if it moves farther north than our models suggest we could see much more rain in the mix.

PS: No luck finding my lost dog Leah tonight...but she appears to be running around in the area around 220th and 64th Ave W in Mountlake Terrace, near the Moose Casino. Let me know if you see her...info on the right...thanks...

Major Snow Event

2012-01-16T15:27:00.000-08:00

This is going to be brief...I will provide a more detailed view tonight.

I have just taken a look at the latest (18 UTC) NCEP (NWS) model runs, the U.S. and ECMWF ensembles, and the runs from major modeling centers (UKMET, CMC, etc). The trend is much more threatening for Wednesday and it appears that we will have a major, highly disruptive snow event.

The big question for days...the question on which the forecast depended on...was where the trough/low pressure would go. Head north of us, we get perhaps 4-8 inches of snow, followed by a few hours of rain and then the whole thing starts melting.    The snow would start around 3-4 AM on Wednesday AM. This is the best case (if you don't like a crippling snow event)

But some models...some very good models...were taking the low farther south, which would extend the period of snow or prevent a turn over to rain altogether. The Canadian GEM and UKMET office were going this way. Then then NWS NAM for the 12 UTC (4 AM) run.   In the 18 UTC run both the NAM and the NWS GFS (normally the best NWS model around her) is taking a more southern route. And the 15 UTC NWS SREF ensembleis doing the same thing (at least the ensemble mean). Ok, this is getting a bit techy..sorry.

The bottom line is that there is a serious threat on Wednesday of 8-15 inches of snow over the region, with a minimal turn over to rain. The biggest snowstorm in years. Anyway, before anyone goes out and buys a snowblower, lets see what tonight's runs show. If they continue this trend then Slushmageddon might be replaced by Snowmageddon.   In almost any conceivable case, Wednesday morning is going to be very problematic for travel...I suspect there will be a lot of school cancellations and the like.

The main roads around Seattle are in very good shape now, but the Wednesday event could dwarf the weekend snow.

More tonight.

More excitement: My lost dog Leah was just spotted near 64th Ave W & 222nd St SW in Mountlake Terrace.

Interesting Differences in Local Snow

2012-01-15T21:16:00.000-08:00

Today there were dramatic differences of snow--even within the City of Seattle--that illustrate some of the challenges of forecasting around here.

Some of you in Ballard and northwest Seattle complained that you hardly saw much snow , while luck denizens of Capitol Hill, perhaps 5-6 miles away, got 3-4 inches in places. Here are a few pictures from Capitol Hill, courtesy of Joseph Chan, a UW undergrad (taken around 2:20 PM).

You notice the Seattle DOT plow on the job! A lot of snow.

It turns out there was a band of heavy precipitation--oriented southwest to northeast- that remained quasi-stationary and crossed the southern part of the City. Here is a radar image at 2:32 PM...see the band?

And here is the estimated 6-h snowfall ending 4: 37 PM from our new SnowWatch application:

As I mentioned earlier, a low pressure area moved down the coast. Then this low moved eastward south of us. During a period in the early afternoon we had a situation with southerlies moving up the southern Sound from this low and other air moving southward towards towards the low from the north. These airflows converged together---like an alternative convergence zone--and caused air to rise...giving us the enhanced snow. Don't believe me? Check out the winds at noon. Notice the winds from the ferry runs in the north and south Sound are in opposite directions. And there was a reversal of the winds aloft.

Enough fun. Some serious weather ahead. Snow will pick up substantially tomorrow afternoon as another upper trough approaches---many will get several more inches on Monday and Tuesday. Here is the 24-h snowfall forecast ending 4 PM on Monday and Tuesday, to illustrate. There will be more Olympic Mt. snowshadowing in the central Sound for this event since the flow is forecast to be more westerely. Of course, this is not cast in concrete and the exact distribution of snow has considerable uncertainty.

Big snow dump in the mountains during the second period! But the bigger story is what happens on Wednesday as a strong warm front approaches.

Dare I show it to you?

Here is the 24-h snowfall ending 4 PM on Wednesday. More inches...and most of that falls in the lowlands in the morning...before temperature surges and it starts to rain.

SLUSHMAGEDDON. A vision that should scare any mayor. And one I am sure will put a smile on the face of KING-TV's Jim Forman. If the warm/low goes farther south than forecast there could be much more snow. Wednesday has the potential to be a very major snow event, but the uncertainty is still large....more tomorrow.

Sunday Morning Snow Update

2012-01-15T09:51:00.000-08:00

More serious snow this morning in many locations....and a very different situation. Looking outside my window in north Seattle the scene is completely white, moderate snow if falling, and there is perhaps 3/4 inch on the ground. Really pretty.

Yesterday the snowfall was quite varied...with nothing to an inch over much of the lowlands, but several inches in the convergence zone (e.g., 3 inches in Snohomish). Here is a snow map 7 AM this morning from the CoCoRahs network (click to expand)

Here is the 24-h precipitation from Seattle Rainwatch--probably corresponds well to the snow distribution right now:

The temperature of the atmosphere is much cooler this morning than yesterday and virtually all precipitation is going to be snow. Here is the latest temperature structure from Seattle SnowWatch:

Now I will show you something NEVER seen before on this blog or anywhere else..the precipitation type output from the dual-polarization capability of the new coastal radar and the old Camano radar. Light blue (DS) indicates dry snow. Remember the beam increases in height away from the radar.

Looking at the radar loops and the latest surface reports indicates a low is now centered south of Grays Harbor--a location that allows precipitation to circle back up into western Washington. At the same time there is a band of snow down the Strait towards Whidbey.
Each forecast run the last few days increasingly suggested this location for the low ...and this morning's run shows it clearly. Looking at the latest Langley Hill radar image we can
see showers offshore circling around and then moving up into western Washington. Snow on the coast, of course. The band down the Strait into NW WA is fascinating...it represents the convergence between southerly flow moving up the Sound and northerly or weak flow moving out BC. What makes it exciting to me is that the models were suggesting this yesterday.

There is a gradient of snow east-west across the Sound..more on the east side, due to Olympic "snowshadowing"

This situation will keep up for a few more hours, but the low and the snow will slowly move south, causing a drying out this afternoon...from Olympia north. Sorry snow lovers!

But the best is yet to come. We will have a break the second half of today and much of Monday. But later Monday afternoon into Tuesday morning another batch of snow will come in with another upper trough and this could be considerably heavier.

And then Wednesday morning we may have snow/rain SLUSHMAGEDON. A very warm, wet system will approach...first we could have heavy snow and then heavy rain. Possibly a big mess.

And remember the mountains are getting lots of snow...over a new foot at Stevens. They needed more snow and will get it. But the avalanche risk will be increasing.

So to summarize: This situation has four stages:

Stage 1: Snow with the front yesterday, with convergence zone snow.
Stage 2: Today's snow with the coastal trough
Stage 3. Later tomorrow snow with another trough
Stage 4: SLUSHMAGEDON on Wednesday AM.

The current model runs suggest that the next week will bring some of the most intense and active weather in a long time...windstorms, rain, snow....the trifecta of NW weather.

Do you Live In or Near Mountlake Terrace?
If so, please keep you eye out for my lost dog..see the picture and more information in the right panel. Thanks. Also message for the City of Mountlake Terrace: Please Don't Pull Down and Tear Up Our Lost Dog Signs!

3 PM Snow Nowcast

2012-01-14T15:09:00.000-08:00

It was an exciting morning...with some wet snow hitting a number of places as the front moved through and the convergence zone formed in its wake. In fact, it is snowing NOW in the CZ near Everett!

The interesting thing is that the air was still relatively warm this morning and afternoon, but evaporation and melting drove the snow and freezing levels down--particularly where intensity was great. A great example of this can be seen at the UW, where the intense precipitation with the front and following CZ cooled the temperatures down quickly (see graphic, third panel down is temperature (black) and dewpoint (red))

As the precipitation ended near Seattle and elsewher, the temperatures have warmed up and now (according to Snowwatch) the freezing level is around 1500 ft outside of precipitation (see below). Remember, that implies a SNOW LEVEL of around 500 ft.

The greatest convergence zone precip around noon was north of Seattle. Look at these surface temps at that time--WAY cooler north of the city where the precip was heavier.

Here is the latest radar image...you can see the convergence zone precip (including snow) over the north Sound and the showers coming in off the ocean (thanks to the new radar!). Snow showers in the mountains.

These showers will continue to move in, and the convergence zone should bring snow to the north Sound for several more hours. Here is a traffic cam near Everett...really snowing there now.

A bigger general snow threat is tomorrow when an upper trough moves in and revs ups the precipitation, with an associated low center moving into the region. It will be much colder then and a few inches of snow could result over Seattle and NW Washington.

Then another disturbance moves in late Monday (more snow!) and then on early Wednesday we could a lot of wet snow as a warmer disturbance moves in, eventually leading to rain. But more on that later.

A Clearer Picture

2012-01-13T22:01:00.000-08:00

Nowcast at 3 PM Saturday. I am going to try doing some nowcasts for this event....first this afternoon.... Just finishing a paper on this subject if anyone is interested. Found here.

We are going into a period of very interesting and active weather.

I have just finished looking over the latest forecast model output from the U.S. and foreign centers, as well as the UW high-resolution simulations, and the conclusion one draws is that most of you are going to see some snow during the next few days--ranging from a dusting to several inches. If anything the threat of snow is greater for the latest series of runs, but they are also emphatic that we are not facing a major, widespread snow event. Instead we are talking about snow showers for many, with a some lowland areas that might get several inches (such as in the convergence zone).

Right now the air above us is quite warm, except for a veneer of cool air near the surface (see plot for Seattle below). A strong inversion caps the cool air, resulting in poor air quality and the current burn ban. No chance of lowland snow with this temperature structure!

But things are going to change rapidly tomorrow as a strong front with very cold air moves through (see figure), with a switch to northwesterly winds behind (see figure). Relatively

steady rain from the front should be over around lunchtime and then with the cold air behind, we will enter the normal post-frontal showers. You could see the front and following showers lurking out there during the afternoon (see image). Interested fact--in the eastern U.S. when a cold front goes by there are few

showers...it dries up. Why? We have relatively warm water out there and cold air over warm water is unstable and produces cumulonimbus clouds. Over most of the continent the ground is cold, and cold air over cold ground does not initiate convection.

The atmosphere will progressively cool later in the afternoon and early evening, with 850 mb (roughly 5000 ft) temperatures dropping below -6C by Saturday evening and -8C on Sunday. Such temperatures are cool enough for snow even with onshore flow...which we will have...Certainly snow above a few hundred feet ASL and down to the surface when there is any real precipitation intensity. By midday Sunday it will be all snow no matter what. North of the border there could be some light snow with the initial frontal passage on Saturday morning, according to the WRF model.

The issue is that most of the showers over lower elevations will be random, hit or miss affairs, except for a few locations where they will be more persistent and stronger. One such location could be the Puget Sound convergence zone that could well develop under northwesterly flow. The CZ could set up anywhere from Seattle north to Everett. Or could be in a band radiating from the Olympics over to Whidbey Island. The exact location is difficult to predict. Here is the latest UW WRF prediction of 24-h snowfall ending 4 PM on Sunday:

And here is for the next 24-h:

This is not snowmagedon, but several inches from Seattle northward, snow over SW Washington, and a foot or more in the mountains. Appreciable snow over NW Washington. You notice a lack of snow over the Kitsap and south of Seattle...that is the Olympic rainshadow with NW flow. The higher elevations of eastern Washington pick up some light snow. Snow comes and goes as a series of disturbances move through during the period through Tuesday. If one of the them is stronger than predicted and sets up a low center over SW WA, we could get much more snow.

But the best is yet to come. In the NW we often get snow going into cold AND going out of cold. The models indicate the mother of all warm fronts to approach early Wednesday (see below--sea level pressure, near surface winds, and temperature in the lower atmosphere--shading). Wow...that is quite a warm front! As it comes in, warm air and lifting will come in aloft. The low level cold air will hold for a short while, giving a burst of snow...perhaps several inches...before it all turns to rain. Just in time for the commute!

And did I mention that the strong winds and moist air is predicted to cause VERY heavy rainfall later in the week. Here is the 48h rainfall ending 4 AM on Friday. Some places...like in the Siskiyous near the Oregon/CA border will get more than 10 inches if this is true, and virtually all the coastal mountains and Cascades will get 5-10 inches. Flooding on some rivers is quite possible if not probable.

Well, after one of the most boring winters I can remember in a while, we are about to start experiencing some interesting times. And with the new Langley Hill radar we will have a new view of the action and should know whether the forecasts are going wrong in time to provide some warnings and updates.

The Upcoming Snow

2012-01-12T11:28:00.000-08:00

Friday Morning Note:
I will do a major update on the weekend snow potential tonight. Plus, a discussion of the heavy rain/flooding threat middle of next week that could start as snow. I talked about the snow situation on KPLU this morning--you can read about it and listen to it at: http://www.kplu.org/
This is the first snow event in which we have the coastal radar and dual-polarization...should be fascinating to watch it unfold.
..cliff

I waited to write this blog until I could "see the whites of their eyes" and this case white is the right color.

It really looks like there will be some lowland snow late Saturday into Sunday...but not the heavy, widespread variety. It is clear that the mountains will get quite a bit during the next week and that the entire region will go through a much colder period starting later on Saturday.

As I have mentioned on a number of occasions, it is easy for the western lowlands to be mild and wet, since most weather systems come from the west, passing over the relatively warm Pacific (sea surface temps around 50F). Sometimes we are cold and dry, when a large high pressure area builds to our west and north. But to be cold AND wet is not easy and requires very specific conditions that are relatively rare.

The key pattern we look for is a big ridge over the eastern Pacific, with a trough moving southward on its eastern side. The trough can't swing too much over the ocean or too much warming of low-level air will occur. Here is the pattern for Sunday morning forecast by the UW WRF model (forced by the NWS GFS model):

You see the basic snow configuration, although it would be better if the flow did not swing out so much over the water. This kind of trough provides upward motion--necessary for precipitation--and is associated with cool air. Close enough to be a real threat.

Here is the surface forecast for 4 AM on Sunday for sea level pressure and lower atmosphere temps and winds:

Cool air (white and blue colors) has moved in behind a Pacific front (which will move through Saturday afternoon with rain.) Generally low pressure centered over northern Washington, but ONSHORE flow at low levels (surface wind vectors shown). This is important...to get really cold we need low pressure SOUTH of us and winds from the north, pulling cold air out of BC. With onshore winds the area will be tempered at low levels even though it is cold aloft. Implication: the possibility of the nemesis of local meteorologists--snow levels of a few hundred feet. I hate it.

At this point in time (4 AM Sunday), the main frontal precipitation is past and we are in the post-frontal shower regime. Above roughly 500 feet, they will be snow. And where the precipitation is heavy enough, snow falling into warmer air melts and cools it...driving the snow level down to the surface.

As you can see from the above forecast, the winds will be westerly on the coast and that could well lead to a Puget Sound convergence zone, which can produce a band of heavier precipitation between Seattle and Everett. There could be an accumulation of several inches in such a convergence zone. This situation occurred on December 18, 1990 where north Seattle got 10-14 inches, with virtually nothing 10 miles north or south of the band. I doubt we will see that much....but a CZ zone event is quite possible on Sunday. Here is the latest high resolution model forecast of snow for the 24-h end 4 PM on Sunday from the UW 4-km model:

2-6 inches over the coastal mountains, 6-12 inches over the Cascades, and several inches over the eastern side of the lowlands. Less in the rainshadow of the Olympics and Cascades. Even the UW 4-km model lack the resolution to get the convergence zone right--on Saturday the 4/3 km forecasts will be available for this time period. And there will be snow over the eastern side of Eastern Washington.

So the bottom line: a very good chance of some lowland snow, but not a uniform heavy snowfall...snow in showers and potential for some accumulation in a convergence zone and the higher eastern suburbs. And with all snow forecasts, there is substantial uncertainty, although several ensemble systems and other forecasts suggest that we can have a lot of confidence in the larger scale patterns.

The timing (Sunday AM) of this snowfall could not be better for Seattle DOT--surely the supplications of Mayor McGinn to higher powers have been answered. I should note that the Mayor's office and SDOT have made a great many preparations for a snow event, including supporting the development of the new snow forecasting application, SNOWWATCH, which I will describe in detail on a future blog.

Forecast for later periods indicate the potential for more snow and perhaps flooding rains. But more on that later...

PS: If you live in Mountlake Terrace or a nearby community, please keep you eye out for my lost dog..see the picture in the right panel. Thanks.

Increasing Threat of Snow

2012-01-10T22:57:00.000-08:00

The new forecast models are increasingly threatening for colder temperatures and lowland snow from Sunday through Wednesday of next week, although none of the forecast are ideal for a truly major event. THUS THIS EVENT SHOULD NOT BE OVERHYPED! At this point we are talking about good snowfalls in the mountains and snow showers over the lowlands.

But you might consider getting prepared: make sure you have chains and windshield decider for your car, be ready to protect sensitive plants-- you know what I mean. The TV stations should get all their colorful parkas cleaned and ready (no KING-5 Jim Forman jokes...yet!). And local DOT folk should stock and make sure their staff are well rested.

On the left is the average of the ECMWF (European Center for Medium Range Forecasting) ensemble forecasts for upper levels (500hPa). The average or mean of an ensemble or collection of forecasts tends to be more accurate than individual forecast model runs. ECMWF has the world's best global ensemble. The right is their single "deterministic" forecast. Both show an upper trough offshore--a pattern very close to the typical western Washington snow configuration. The U.S. model, which initially was much less threatening, has now come much closer to the ECMWF solution. Snow forecasts are always uncertain because it is difficult to be cold and wet west of the Cascades at low levels. The move to colder temperatures is MUCH more certain.

Our high-resolution regional models, forced by the NWS GFS model, indicates some snow (light) on Sunday, and a more serious threat Tuesday, but there is lots of uncertainty, of course, at this range. Below is the 24-h snow prediction ending Monday at 4 PM. Lowland snow in the forecast, especially over southwest Washington. There is a significant possibility of a convergence zone snow even (Seattle to Everett) late on Sunday into Monday. Will watch out for this!

The mountains are going to get it..no doubt about that...which is very good news for skiers. Wax your skis!

KBTC-TV aired a nice segment on the new coastal radar, click here or below the picture to view it.

http://www.kbtc.org/page.php?id=657

Winter Over? Don't Bet on It!

2012-01-09T22:06:00.000-08:00

Bicycling in today, I marveled how spring-like it was. Mild temperatures well above normal. The grass is really growing--starting much earlier than normal. At the UW, I could see large number of bulbs pushing up in the beds. And it has been warmer than normal for weeks now--take a look at the comparison between Sea-Tacs temps and normal:

The normal high is around 45F and we have been hitting 50F and beyond on a regular basis. Very good for my lost dog.

The National Weather Service extended forecasts have repeatedly called for a return to normal La Nina conditions--wetter than normal and colder than normal--but it simply has not happened. However, the latest batch of forecasts from both the U.S. National Weather Service and the European Center for Medium Range Weather Forecasting suggest the possibility for a change to much cooler temperatures. And in the meantime we will have a period of very little precipitation and even some sun.

The European Center for Medium Range Weather Forecasting (ECMWF) is the gold standard for short and medium range weather prediction. They have about a day more predictability than the NWS forecast center. This is completely embarrassing, unnecessary, and a national disgrace. And a topic for another blog.

My rule is that I don't get too excited until the forecasts get within 120h (Saturday morning)--so here is the 120h forecast from ECMWF for upper level heights (500 hPa) and 850 hPa (roughly 5000 ft) temperature. Cold air (blue/purple) to our north and a trough just offshore. This is a threatening pattern for cold/snow.

The forecast for a day later is certainly of concern...cold air is closer, as is the trough.

The NWS model slides the cold air past us to the north...and we are just on the edge in the ECMWF prediction. The ECMWF ensemble mean forecast (averaging a large number of predictions for the same time) has a very similar pattern.

The bottom line---we have several dry days (guaranteed), but will have to watch the situation carefully this week. The forecasts are on the edge past Friday. We could end up with nothing or snowpocalypse. We will know in two days.

We are still in a La Nina year and remember last year (also La Nina)...warm in January and then we froze over in mid-February. But also keep in mind we really only have 6 weeks left of winter. By the end of February, winter is really over in the lowlands. Snowpack in the mountains can still pile up into early April.

Searching for Leah

2012-01-07T14:44:00.000-08:00

For nearly four months, I have mentioned my lost dog Leah in this blog. We have not recovered her yet, but we know she is still alive and roughly where she is. The story has become quite a tale, one with both villains and heroes. A story of an amazing journey and survival in the wild. And it has implications for many of you with pets and speaks to the need for new approaches for dealing with a significant problem.

Leah is a 9 year-old female, black cockapoo (with white markings) and has tags and a microchip. In September, we went on a short vacation and left her with a "professional" pet Nanny in northwest Seattle --someone recommended to us by an acquaintance and who received a good review on Yelp (more on Yelp issues later). Needless to say, my family loves this sweet little dog.

A few days later, while were still away, the pet Nanny called-- our dog and several of her other charges had escaped from her backyard. The other dogs were retrieved, but our Leah was gone. This was a person who promised that the dogs would never be left alone outside the house. She couldn't understand how the gate got opened and even blamed the "meter man." This was Saturday, September 10th. The next day she still had not found Leah and we tried something high tech--robocalls to the neighborhood asking for help. No response. On Monday, we were back in Seattle, driving the neighborhood. Day after day we searched, putting up signs over a wider and wider radius. Placed ads on craigslist. Went to all the local animal shelters. Local community online newspapers were wonderful, giving her lots of publicity. Nothing.

We got in touch with the most wonderful organization, one that will play a big part in this story: missingpetpartnership, a group dedicated to finding lost animals. I cannot say enough positive about these folks. One thing they stressed--to find a missing dog you need signs, BIG SIGNS, and lots of them. Signs with big letters, big pictures, bright colors. And we did exactly what they said. I have made hundreds of signs when I am not blogging!

Several weeks passed. Nothing. And then at the end of September something unexpected happened. We got a call from someone in Mountlake Terrace, many miles away, who had spotted one of our signs in Seattle. They were sure they had seen Leah outside of an insurance agency in Mountlake Terrace. Could Leah have walked roughly ten miles through a highly urban area to reach this location? (the map below shows you the route she probably would have taken).

By that time we were working very closely with missingpetpartnership (MPP) and particularly two of their members--Jim and Chris. Jim had a tracking dog named Kelsey and they came up immediately, using one of Leah's old blankets to provide the scent. Kelsey confirmed it was Leah and Jim traced her route from the insurance agency into and out of nearby Terrace Creek Park. My wife walked with Jim...it was strange to walk in Leah's path...past bowls of food placed in backyards other animals. But Leah was alive.
The pet nanny that lost the dog refused to help us in Mountlake Terrace.

Jim told us that dogs often head north when lost and looking at the map we think we figured out her route...she probably followed the Interurban Trail, around Lake Ballinger (water supply), through Nile Golf Course and took a wooded and quiet route across I5 (228th St). (see map above)

Terrace Creek Park had plenty of water, many houses bordered on the park, with bowls of food for outside animals and dry sheds. Lots of cover in the park. And some people were leaving food out for feral cats.   Ideal location for a little dog to survive--except for possible coyotes.

We began an intensive campaign. We placed dozens of signs near major roadways. Chris of MPP put out dozens more. We tried the robocalls again for that neighborhood. And kept up visiting local shelters and all the online services.   We started getting more and more calls of people claiming to see her (many several days after seeing her unfortunately). Some were obviously other animals, but some were clearly Leah. Chris helped organize an "intersection alert" where we and volunteers from their organization waved signs about Leah and gave fliers to passing motorists. My wife is up in Mountlake Terrace multiple times a week searching for Leah. What extraordinarily kind and generous people to spend their free time, waving signs in the cold to save a lost animal.

This situation continued into November--Leah was moving in and out of the park and the surrounding neighborhoods where we got intermittent reports, but we could not get her. We put up infrared cameras in spots where the tracker dog suggested she had visited, with food and our scent items to attract her.   The food disappeared and we got nice pictures--but of neighborhood cats! We put out a trap with food....but to no avail.

Through this period I developed a detailed knowledge of the lost dogs and cats of the area from Craiglist and shelter lists/visits. One day visiting the PAWS shelter in Lynnwood I saw a dog matching a description on Craiglist and called the owner, a match! At least one lucky family was reunited with their dog. And it made me think we need a better system for dealing with lost animals.

In early November, we got more reports--from the Moose Casino on 220th St SW. For several days, Leah was hanging around the back of the Casino (We wish we had known!) and even scored a burger from a kind casino worker. One of them saw our signs and called and we headed over immediately. My wife and I spent hours in a cold car watching for Leah to return...no luck.

Mountlake Terrace started pulling down our signs. First, they said we couldn't have signs on poles because advertisements aren't allowed (as if lost dog signs are advertisements) and that our signs would be a problem for utility folks (right!). Then we switched to signs in the ground and they took those away (and destroyed them)...claiming the city banned signs not only on immediate stree right of ways, but even well on the home side of sidewalks. Very nice city officials in Mountlake Terrace. I mentioned the situation to my colleague and friend Jeff Renner of King TV--he was outraged and suggested we contact (and he emailed), Jesse Jones...the KING TV consumer advocate. And Jeff cc'ed the Mountlake Terrace folks with the idea of bringing in Jesse. Funny, they became a modicum more reasonable and slowed down their removal of our signs. (It would have been hilarious if Jesse showed up at Mountlake Terrace town hall...Jeff called it "City versus Puppy".

The Threat of Jesse's Intervention May Have Helped Soften Mountlake Terrace Officials That Don't Seem to Care About Lost Dogs.

During December we put in some ground based signs and started getting more reports...and of course we were up there on a daily basis. More reports. Some people would see Leah and she would run away. Jim of MPP tried to track her. No luck. Last week, Leah was seen near Cedar Way and 236th SW (Markland Apartment)--she came up to someone's back door and they called us. My wife happened to be up there and was at the location within 10 minutes...no luck.

Our little dog is afraid and skittish, but she is a survivor. Hopefully another call will lead to one of us seeing and retrieving her. We have staged food and scent articles, which hopefully will attract her, and will try a trap again.

This whole adventure has been an education for me. I now realize how many dog and cats are getting lost, and how ineffective the current system is. Some shelters take in animals and don't list their charges or put their pictures online. There a number of lost animal lists, none of the coordinated. Various municipalities have separate animal control officers/offices that don't communicate well outside their district. People try ineffective means (e.g, small signs) to find their animals and public lists (like Craigslist) are not set up to deal with the problem (e.g., some people refuse to describe the lost animals they find! and the items age off too quickly). We need ONE regional list of lost/found animals and ALL lost/found pets must be photographed, with their essential information online. Municipalities like Mountlake Terrace must learn how to be more helpful. And people should insure that they microchip their pets, plus have tags.

Some people might think this is an unimportant problem, but pets are like family members, and their loss is really devastating to those who love them. And to allow these intelligent, sensitive creatures to be drifting on the streets is simply wrong.

I would like to thank many of you who follow my blog for helpful and sympathetic advice and support. Chris and Jim of MPP, who have been such a huge help to us. MPP is an organization that deserve the support of animal lovers. And Kathy of the Feral Cat Society, who has helped immensely with the search.

PS: Another thing I learned from this situation is that one can not trust YELP. I put a negative review of the pet nanny. Initially it was online, but then strangely enough it was removed. Put it back. Same thing. They have a secret algorithm for removing some reviews--particularly highly negative ones. Very questionable practices.

The Other Heat Wave

2012-01-05T20:19:00.000-08:00

TV Notice: KBTC TV (One of our local public tv stations) will be doing a special on the Langley Hill radar on Monday, Jan 9th at 6:30 PM. More information here: http://www.kbtc.org/pop_schedule.php?id=22977

Yesterday, there as also another local heat wave....one related to the Eatonville heat burst: several locations in eastern Oregon and Washington got into the upper 60s, with downtown Walla Walla hitting 72F. Here is the official record report from the NWS:

Warm air aloft, strong southerly winds, and terrain are the cause--just as the case for Eatonville. The north side of the Oregon Blue Mountains can get real toasty, even midwinter, under such conditions, with the towns of Walla Walla and Pendleton in the banana belt. Here are the observations at the Walla Walla Airport (KALW). Temps start in the 30s in the morning (time in GMT/UTC-1553 is 7:53 AM), temperatures surged into the upper 60s in the early afternoon when the winds switched to a southerly direction (direction in degrees, 180 degrees is southerly, 90 degrees is easterly, etc).

As shown by the following terrain map, southerly or southeasterly flow descends the Blue Mountains, warming by compression.

Exceptionally boring weather is ahead of us...relatively dry, seasonal temperatures, no major storms.

Eatonville Heat Wave

2012-01-04T21:57:00.000-08:00

This morning, one area of western Washington warmed into the lower 60s, with brisk southerly winds--more like Hawaii with strong trade winds than western Washington in midwinter.

The location? The area around Eatonville (near the SW entrance to Mt. Rainier). Here is plot of the weather conditions there (time is in GMT, so 1256 is 4:56 AM). Temperatures were in the 50s overnight and rose to 60F at 5:55AM! Temperatures help up until 1855 GMT (10:55 AM), after which cooling occurred. Why so warm? Hint: look a the winds. Winds turned southerly and were strong at the temps rose.

Take a look at a plot of the observations around 10AM. There was a whole region of warmth around Eatonville that extended toward Enumclaw and southwestern Tacoma. At the same time that Eatonville luxuriated at 60F it was only 42F at Renton. I could make a Renton joke here but will fight the urge.

We can get an idea of the type of air moving into the region by looking at the radiosonde upper air observations at Salem, Oregon--see below. Strong winds from the southwest and quite warm air aloft (12C,54F) above colder air near the surface.

And what is immediately upstream of Eatonville? Substantial terrain, reaching 3-4 thousand feet, as show below:

Now we can put it all together. Strong, warm flow approached the terrain south of Eatonville and then descended toward the town. Cool air near the surface was swept away and the downsloping air warmed by compression (adiabatic warming is the term in the weather biz). Turns out that our high resolution models had a good idea of this...here is the 12hr forecast from the super high resolution (4/3 km) UW WRF model:

Theorange/ reddish colors are the warmest.

I should note that both sides of the Cascades have been far warmer than normal lately--with low temperatures close to the usual highs. Here is the proof for Sea Tac and Spokane:

Temperatures should cool down later this week. And keep in mind that last January was also mild, but was followed by super cold air in February.

Tonight's Political Commentary

Senator Rick Santorum, who is now so much in the news for surging in Iowa, is well known to the meteorological community, and not in a good way. In 2005 he introduced the National Weather Service Duties Act that would have prevented the NWS from providing the public with any weather information when private-sector entities perform the same function commercially. It appeared he was trying to help a business in his district, Accuweather, gain a huge market. In September 2005, Santorum criticized the National Weather Service for its evacuation warnings given for Hurricane Katrina, saying they were "insufficient" and said the public suffered "serious consequences" when they fall short of "getting it right. Just nonsense...the Katrina warnings were the strongest I have ever seen.

Dog News

My little Cockapoo was AGAIN seen in Mountlake Terrace near an apartment complex (Markland Woods Appt) in the vicinity of 236th SW and Cedar Way. If you live in the area, keep an look out!

Virga!

2012-01-02T21:34:00.000-08:00

Tonight the wind is blowing outside as another trough passes by...in fact, wind gusted above 50 mph at some exposed locations near water. But in this blog, lets talk about something much more benign...

On New Year's Eve lots of folks were at the Space Needle to watch the fireworks display and it was precipitating....but not at the ground. At ground level it was completely dry at midnight, but precipitation was falling from the clouds above and evaporating before it reached the ground--that's virga.

We had a few ways to tell that precipitation was falling...the Camano Island radar--whose lowest beam is about 2000 ft above the city--showed the precipitation at midnight (see image):

The vertically pointing Seattle profiler also showed precipitation falling from above and evaporating. But at the surface there was nothing until 1 AM. Here is the observations at Seattle-Tacoma Airport:

L- at 0853 UTC (12:53 AM PST) was the first precipitation report--even though the radar had showed precipitation for a few hours. Earlier in the evening there was a large difference between the temperature (lower 40s) and the dewpoint (mid 20s) at this location, indicated low relative humidities. In fact, here is the plot at the UW...the air got drier and drier during the period before midnight (the RH is found in the fouth panel down).

During the day you can see virga...here is an example:

Virga is often noted around here during the beginning stages of precipitation events. And having dry air at low levels helps insure precipitation evaporates before reaching the surface. The deeper the dry air the better. West of the Cascades a situation with easterly flow at low levels with moist, southwesterly air aloft is a good virga producer, and is one that often occurs as storms approach us from the west.

From below, the clouds lose their hard edges and there is a "softness" to the underside of the clouds during virga periods. Sometimes you can fell a cool chill at the ground as the air, cooled by evaporation, reaches the ground.

Anyway, virga might be a .5 on the meteorological Richter scale, but still is worthy of note.

Finding Sun

2011-12-31T09:08:00.000-08:00

During this time of the year there are few more important questions for sun-starved Northwesteners. How can one get to sun, either in the car, or in the shortest plane ride possible? This blog will provide some guidance.

We start with the problem. The western side of the state is one of the cloudiest places in the country during the winter and the "bowl" of eastern Washington often fills with low clouds. Plus, we are fairly far north and thus days are short. Fortunately, a little bit of meteorological knowledge and online access to satellite imagery can help you get to sun on many days with a modest drive even when your home is in the murk. And sun is nearly always a short (and inexpensive) plane ride away.

Step 1: Find a good online satellite imagery source

To find sunshine, you need to view satellite imagery--and particularly visible satellite animations. There are a number of good sources of such information, but one I recommend is provided by the National Weather Service: http://www.wrh.noaa.gov/satellite/?wfo=sew
There are many others, including my own department web site. If we are in an unusually sunny situation you will be able to determine that from such imagery. If sunny, don't proceed any farther and GET OUTSIDE ASAP TO ENJOY IT!

Step 2: There are clouds in your area and you want to see if there is
some nearby sun. No problem.

If there is strong southwesterly flow, then check for a cloud-free zone to the northeast of the Olympics, roughly between Port Angeles to Port Townsend, and yes Sequim. Sometimes the clearing stretches to Victoria and the southern San Juans. An example is shown below. You see this...you know where to go! In fact, there is an entire web site dedicated to this cloud free zone (http://www.olympicrainshadow.com/)

But there are plenty of times the entire western side of the Cascades is full of clouds. What do you do?

If the flow is more westerly, then there might be a convergence zone over central Puget Sound. It is pouring and raining over Seattle--depressing! But the convergence zone is narrow...a short car drive north and south will get you into sun? Don't believe me? Check out the satellite picture from yesterday. And with westerly flow there is often sinking flow and clearing skies over the eastern slopes of the Cascades--Cle Elum, Wenatchee, Ellensburg, or Yakima could be in bright sun even if the rest of eastern Washington is in the murk (see same image).

Or during periods when high pressure is overhead and flow is weak, the lowlands of western and eastern Washington are in low clouds, but the mountains are clear (see below). What do you do? Head up! Go for a hike or do some skiing. Or just drive up there with some suntan lotion. Here is an example.

Step 3: The Northwest is completely cloud covered from a major storm. And you want warm temperatures and sunny skies. Where do you go if you can't afford to fly to Hawaii or Cancun? No problem. Head to the desert southwest of the U.S. Take a look at the number of hours of sun in December in the graphics below (red is most, dark grey is least). The U.S. southwest is amazingly sunny mid-winter. The worst place (us) and best place (SW) are only about 1000 miles apart! Palm Springs, Tucson, etc. are very safe bets for mid-winter sun...and you can find relatively inexpensive fares (order of $200 RT).

So the bottom line: using a little meteorological knowledge can go a long away to avoiding Northwest winter blues from lack of sunshine.

Subtropical Moisture, Record Lost, and Thank You

2011-12-28T21:54:00.000-08:00

First, the thank you. I very much appreciate the contributions of over one hundred of you to my weather research fund. It has allowed me to fill in the financial holes for running the local weather prediction modeling research, helping to make up for losses as funding agencies reduce support. Furthermore, I am dedicating $2000 of the support for an undergraduate Weather Research scholarship. As an instructor and the department's undergraduate adviser, I see first hand the impact of the rapidly rising UW tuition, with many of our undergraduates acquiring large debt levels and working more and more hours--leaving less time for study and sleep. The most extreme case of this was one student that kept on falling asleep in my junior synoptics class. I talked to him one day about it...turns out he was supporting himself by fueling jets at Sea-Tac airport overnight! Anyway, as long as the contributions come in I would like to continue using a portion of the funds for scholarships. And thank you to all of you that have sent me tips and suggestions about my lost dog Leah. She is still roaming around Mountlake Terrace and it is maddening that we have not found her yet.

Today, it was warm, moist and balmy---the warmest and wettest day in over a month. Many locations in western Washington reached the mid-50s, as subtropical, southwesterly flow surged into the region. As apparent from this satellite-based vertically integrated water vapor content image, the moisture plume did not come from near Hawaii, but pushed westward and northward across the north-central Pacific (purple and red, highest values, followed by orange and yellow). This is a modest atmospheric river with origins in the subtropics.

The plume most directly intersected the coast south of Washington on the northern Oregon coast, and thus the higher precipitation amounts were to our south. Here is the 24-h precipitation totals ending 9 PM on Wednesday. Values ranged from a trace (.01 inch) in the middle of the rainshadow NE of the Olympics to 3-5 inches on the western slopes of the Olympics, coastal mountains and Cascades, with particularly large amounts over NW Oregon. Talking about rainshadows, amazing low values in eastern Washington (trace to a few hundredths of an inch).

And as long as we are talking rainshadows...here is a radar sample during the early afternoon, when the shadow was centered near Everett. You got to love living around here---you can be completely dry at one location, but pouring a short car drive away.

A weak disturbance comes in later tomorrow (Thursday), a stronger system on Friday, and believe it or not, a relatively dry New Year's weekend is ahead. A very normal situation.

Finally, the rainfall today has prevented Seattle from enjoying the driest December on record---we did have the driest first three weeks on record, though. But the drought and the west coast ridging that produced a mainly dry December has resulted in the western U.S. snowpack being well below normal. Here is the latest snow water equivalent chart, giving the % of normal. Washington is now mostly 70-100% of normal, Oregon about 50% of normal, and the CA Sierras down under 20%. Want above-normal snow? Head to Arizona and New Mexico!

The Christmas Day Storm

2011-12-26T11:32:00.000-08:00

Yesterday brought quite a blow to portions of westerns Washington, with gusts reaching 50-65 mph, loss of power to tens of thousands of people, and the tragic death of a young girl. It is also an event that was underplayed by the National Weather Service, although they did have a Gale Warning out for the coast and NW waters. This is an example of powerful winds associated with a very strong frontal passage, rather than an intense low moving to our north. There is a lot to discuss.

So how strong did the winds get? Here is a list of a few locations. One unofficial spotter at Three Tree Point near the Sound reported a 63 mph gust. For many locations, the winds yesterday were the strongest over the past year.

Spd(mph) Time(PST) Location
----------------------------
60 ~11:30 Alki Point Light
56 11:32 Bellingham Airport
54 11:31 Whidbey Island NAS
58 9:21 Smith Island
56 11:46 Paine Field
54 11:45 Edmonds Marina
58 11:22 West Point Light
53 11:50 Evergreen Pt Bridge
41 11:28 Boeing Field
53 11:16 SeaTac Airport
43 11:50 Renton Airport

and..as noted in a comment below, 122 mph at Camp Muir on Mt. Rainier!

Here is a plot of the hourly winds at Seattle's West Point. You will see how quickly the winds rose, peaked, and dropped and the very intense pressure trough (large pressure drop before the highest wind, followed by an intense pressure rise). Green is pressure, blue sustained winds and red are gusts.

Imagine taking a ferry ride across the Sound? Here are the winds from the Edmonds/Kingston ferry. SUSTAINED winds of up to 47 knots (54 mph)! The would been an exciting trip.

This wind event was associated with a strong front, one that was unimpressive in terms of precipitation, but one with a very strong pressure trough and wind shift. It is also an event that new coastal radar provided a lot of hints of possible strong winds.

Here is a forecast from the UW WRF model (initialized at 4 PM on Saturday) for 7 AM on Sunday. Very sharp front. Large north-south pressure difference and strong southerly winds in front of it. Very sharp wind shift to westerlies behind it.

Let me show you the forecasts from the high-resolution (1.3 km) WRF model at 10 and 12 PM showing predicted gusts (knots). Much stronger winds over and near the water, with some gusts reaching 40-50 kts. Not perfect, but certainly suggests a strong event.

But what about our new coastal radar near Hoquiam? Did that tell us anything as the front approached? I rarely show you the Doppler velocities from the radars, but I will now. The color indicate the speed of the air towards or away from the radar. Here are the winds at 9:12 AM. The sharp color contrast indicate very powerful southeasterly flow on the cooast and a very strong frontal wind shift immediately offshore. This was a powerful front.

In addition, coast observations, such as at Destruction Island, indicated an unusually intense frontal passage, as shown below.

Anyway, a good example of what a strong frontal passage can do and the strengths and limits of our technology. An example of why we need more effective nowcasting--short-term diagnosis and forecasting. And one more thing...there is a lot of action predicted for this week...so keep tuned.

The Big Shift in Our Weather

2011-12-23T10:35:00.000-08:00

Mother nature has a holiday gift for you--a major shift in our weather pattern. For roughly three weeks, the Northwest has been preternaturally dry, you would think we were living in Palm Springs! For example, Seattle-Tacoma airport has only received .25 inches this month, 3.61 inches below normal. Yesterday, sun was nearly everywhere and seasonal affective disorder (SAD) cases are surely down this winter.

It all ends this weekend.

Instead of the high-amplitude, persistent ridge in the eastern Pacific the atmosphere will transition to what meteorologists call zonal flow, in which the jet stream, and the strong flow associated with it, head straight into our region. Embedded in this flow there will be low pressure systems and fronts that will bring rain and wind every day or so. Temperatures will warm into mid-forties each day, clouds will never leave us, and fog and frost will be far less likely--normal weather for us mid-winter.

I am deathly afraid that this pattern will end our chances of being the driest December on record.

Just to illustrate, here are two upper level maps at a level where the jet stream is generally strong (300 hPa, roughly 30,000 ft) for today and next Wednesday. The shading gives the wind speeds. See the difference? Ridge versus zonal flow. You can think of the jet stream as the atmosphere's fire hose....and we will be on the receiving end.

With strong zonal flow it becomes increasingly difficult to get the timing of weather systems right--so don't be surprised if forecasts are off by 6 hrs or so, particularly for forecasts a few days out.

On vacation and want to escape this onslaught? Can't afford the exorbitant fares to Hawaii? Head to southern California. They will be sunny with temperatures heading into the upper 60s and 70s. No rain. Lots of sun. Ironically, the ridge has brought us the dry, sometimes sunny weather, produced cooler than normal conditions in the SW U.S. since there is cool northerly flow to the eastern side of the ridge. But with the ridge gone, southern CA temperatures will rebound.

And one more holiday gift....nearly all the long-range models indicate La Nina will disappear over the summer and next winter will have a very different character.

Happy Holidays....

Where is La Nina?

2011-12-21T21:13:00.000-08:00

A number of you have commented or emailed the same questions and comments that run like this:

" I thought it was a La Nina year--aren't they supposed to be wetter than normal"
"The National Weather Service said this fall would be wetter than normal--boy did they mess up!)

December is turning out to be one of the driest on record--in fact, there is a chance it could be the driest December since record-keeping began at a number of western Washington sites.

Take a look at the precipitation at Sea-Tac for the past 4 weeks (blue is normal, red this year):

Amazing...precipitation has almost been flat-lined since December 1--we are about 4 inches below normal, with only about .25 inches this month.

In general, La Nina years are wetter during the entire fall-winter season....but that is only on average. You can think of weighting a coin---instead of heads and tails being equally probable, heads is more likely. Throw the coin ten times and it could be heads eight times--BUT you STILL will get two tails.

This year it is more LIKELY to be wetter than normal, but some La Nina years HAVE been drier than normal.

Here is a plot that summarizes the situation for Washington State. The dots representation individual years, which can be El Nino (red), neutral (green) or La Nina (blue) years. The y axis gives the precipitation amounts for October through March. Yes, the blue (La Nina) years typically have more precipitation than the other years. But there is a considerable range for the La Nina, El Nino, and neutral years, with a number of La Nina years being relatively dry. This year may well be one of them--although it is too early to know what the final winter's total will be.

You can think of NWS forecasters as casino operators---over a period of time the house will win, but occasionally someone can walk away with a jackpot.

But there is something else... a characteristic of La Nina years is the persistence of a major ridge in the eastern Pacific (see NWS graphic below). Normally, that ridge is far enough west that we are in the

downstream trough...giving us cool, wet weather. This year, the trough has been farther east than normal...giving us drier than normal conditions. And we have seen the ridging day after day. For some reason the ridge is shifted--and so we have been generally dry and cool.

The current model runs show a return to more normal, wetter conditions soon.

The Surface Data Revolution

2011-12-19T21:45:00.000-08:00

An important change has occurred during the past decade that many are not aware of: a huge increase in the number surface observations. Go back 20 years ago and there were perhaps 1000 regular observations around the U.S., mainly at airports. Roughly 30-40 regular observations over Washington State at primary and secondary airports.

In contrast, today there are certainly at least 100,000 surface stations that report hourly and distribute their data in real time via the Internet over the U.S., and several thousand such observations over Washington alone. In fact, there are so many observations available today, that if we plotted them all the weather maps would turn black with them over many parts of the Northwest. Here is an example from earlier this year--there are a lot more stations available now:

So what has happened to provide such a treasure drove of information?

First, there are many groups in the observing business right now...organizations that for whatever reason have established real-time observation networks. Some local examples: Seattle Public Utilities, the State AgWeatherNet, Washington State Ferries, Washington DOT, local private utilities, NW avalanche network, School Weather Networks associated with local TV stations, etc.---the list is long. And then there are hundreds, if not thousands, of Northwest residents that has purchased capable weather stations and made their data available in real time via the WeatherUnderground or similar online services.

Which gets to the other parts of the revolution: the availability of very good amateur equipment (like the Davis Pro weather stations) and the omnipresence of the Internet. So for a very modest investment one can collect excellent quality information and make it instantly available to the world (something impossible two decades ago).

At the UW we collect more than 70 networks in real time, quality control and archive them, and make them available to all of you at our web site, Here is a sample for Seattle right now (and our system does not plot every observation!):

Interestingly, there are some places where there is several stations within a half mile, while gaps remain in others.

This huge amount of surface data for the first time gives us insights into the local variations of surface weather features. And enhances our ability to do very short term forecasting---called Nowcasting. The national weather service also collects another of weather networks, through their MADIS system, and you can get at a lot of this information via their very nice web site:

http://www.wrh.noaa.gov/mesowest/gmap.php?map=sew

And this surface data revolution is just warming up. Some new smartphones take continuous pressure measurements (as a way of getting height)--can you imagine if that data was communicated to a central site in real-time? And it is matter of time before all cars have internet capability--imagine if each reported temperature and other weather parameters in real-time as they drive around. And there is more.

Although surface data is very useful, it is not enough. Meteorologists need 3D data to forecast the weather since we need to describe the atmosphere's entire volume to run our models into the future. And surface data often has problems--wind sensors placed behind an obstacle, temperature sensors too close to a building or not properly shaded; the potential issues are many.

Securing huge volumes of upper air data is another revolution...but one that will wait for a future blog.

How is the snowpack doing?

2011-12-17T08:46:00.000-08:00

The short answer: not too good. Something that is surprising in a La Nina year, when snowpacks should be above normal.

Take a look at the latest snow water equivalent map for the west (this is the amount of water in the snowpack compared to normal). The Cascades are near normal due to the considerable fall received last month--but that snow is aging fast. Oregon and Idaho: well below normal. California's Sierra's are roughly 25% of normal. You want snow?--head to Arizona and New Mexico, where some locations are nearly 300% of normal. This is due to the frequent troughs and cut-off lows that have moved into that region due to the persistent high pressure over the eastern Pacific.

Talking of persistent---current models suggest the east Pacific ridging will remain in place at least for the next week--although with weaker amplitude. This will allow occasional weak fronts to move through--such as the system expected tonight and Sunday morning. Here is the latest 6-10 forecast from the National Weather Service's Climate Prediction Center---dry over the west. With such east Pacific ridging, a lot of our moisture is going into Alaska, where they are getting hammered.

Here is the upper level chart for Christmas Eve. The ridge is so large and high amplitude, Santa will be blown way up into Alaska. Favorable conditions for dropping down a chimney---nice and dry.

Talking of snow conditions, the frequent periods of clearing over the mountains have led to frequent deposits of hoarfrost (see picture below). The is important because when snow does return, such frost result in an underlying weak layer that could lead to avalanches. But we can worry about that later.

Drought

2011-12-15T07:30:00.000-08:00

The Driest First Half of December in Seattle History!

Extremes of any type are interesting and right now we are in the midst of an unusual December drought. At Sea-Tac Airport as of Wednesday night we had only gotten .03 inches so far this month, 2.51 inches BELOW normal. Spokane has had .02 inches, 1.09 inches below normal.

Checking out the record at Sea-Tac, it appears that we have experienced the DRIEST FIRST TWO WEEKS ON RECORD at that site. Wow.

Perhaps the best way to appreciate the situation is with maps showing the percent of normal rain over the past 14 days. Reddish colors indicate less than 25% of normal. Most of the west is red! And a great deal of the West had less than 5% of normal for the past two weeks.

Or you can look at the departure from normal precipitation over the period (see below). We are down more than two inches over the entire western side of the Cascade, with far larger deficits in the mountains.

There is some light rain this morning, but that won't be enough to change the story much. By 7 AM Sea-Tac has received only .02 inches and the Langley radar shows nothing offshore. The problem, of course, is the extraordinarily persistent ridge over the eastern Pacific....and though ridge is weakening a bit (allowing some weak and splitting systems to influence us), it should still be in place for a while.

The other side of the coin is that we have been unusually cold... here is the difference of the maximum temperature from normal for the past two weeks...virtually all of Washington State except the Cascades and the eastern slopes are well below normal (by 3-6F). Some folks are claiming we will have the driest or coldest December on record....I think they are premature.....but the first half has certainly been unusual, and a contradiction to at least one expectation of La Nina, during which entire winter season is usually wetter than normal.

My Lost Dog: There have been several more reports of my dog in Mountlake Terrace...if you live up there and see her, please let us know RIGHT AWAY! (contact information at the right). She has been living as a wild animal for nearly three months now. Either someone has to take her in and call us, or we need a fresh report to rush up there immediately. Of course, we have been searching ourselves a great deal. An issue is the town of Mountlake Terrace, which has been tearing down our signs even when they are on private property.

Surface, Air, and Soil Temperatures: The Differences Can Be Large and Important

2011-12-13T17:44:00.000-08:00

Meteorologists have more than one temperature reported at or near the surface and knowing the difference between them can save your live or your crops.

This blog will describe them and show you some recent examples.

First, some temperature 101! When a TV weathercaster gives the temperature at some location (Sea-Tac, Portland, Wenatchee, Forks, etc) or you get the temperature from some weather web site or app, at what height is the temperature? The answer is generally about 2 meters (roughly 6 ft), the standard height used for temperature sensors (here is the NWS temperature sensor--the white thing with the dome top):

When you get an air temperature from the sensor in your car, the height is generally about half the official height...roughly 2 feet.

Some locations measure the surface temperature---the actual temperature of the surface. Sometimes they use a sensor in a road or on the surface of the ground, other times they use infrared thermometers--like the ones used in doctor's offices to measure the temperature in your ear. Here is an example--they are called infrared radiometers:

Finally, a number of weather observing sites, particularly agriculturally oriented locations, measure the soil temperatures at one or several depths:

Now here is the interested part---these three temperatures... measured only feet apart in the vertical...can be very, very different, and the differences depend on season and time of day.

During a relatively clear, low-wind period, like we have had the past few weeks, when there is good radiational (infrared) cooling to space, the ground cools off rapidly at night. In such situations, the 2-m air temperature can be 2-8F warmer than the surface. On the other hand, temperatures in the ground are generally much warmer in such situation, and the deeper you go the warmer the subsurface gets. On the other hand, during the day, and particularly during the summer, the surface gets heated by the sun and can be MUCH warmer than either the air temperature or the ground temperature.

Not many locations have all three sensors (air temperature at 2 meters, surface temperature, ground temperature). One network that has both soil and air temperatures is the Washington State AgriWeatherNetwork, run out of WSU in Pullman (a wonderful collection of data and a great investment by the State). Here are the air temperatures (2-m) around 10 AM this morning...20s in eastern WA and low 30s in the west.

Take a look at the soil temperatures at 8 inches into the soil. MUCH warmer...low 30s in the east and mid to upper 30s in the west...even some low 40s. Why are the soils warmer? It takes time for the cold to spread into the soil.

To show this, here are the soil temperatures for the AgriWeatherSite in Woodinville over the past month. A general slow decline in temperatures over the past two weeks of cold from the mid-40s into the upper 30s. The daily heating/cooling cycle is really damped down in the soil. The farther you go down, the less daily temperature change.

What about the surface temperatures?

Here is a comparison of the surface and air temperatures at Marblemount, Washington for the past few days (times in GMT):

During the night, the surface temperatures (blue line) can be 5-7F less than the air temperatures, while during the day, the air surface and air temperatures are more similar, with the ground temperature even getting warmer for a while.

Last night I went outside with an infrared radiometer measuring the surface temperatures outside my house and comparing it to the 2-m air temperature (which was 30F)--yes, my neighbors are used to my quirky behavior. My concrete driveway was 27F and the grass was around 25F. Why was the concrete warmer? It was getting some heat conducted up from below, while the grass had some air space below to lessen upward conduction of heat.

Can this information save your life? You bet. As I have mentioned before, the greatest weather threat to your life is probably roadway icing. On cold, relatively clear nights, the road surface temperature can easily be a few degrees cooler than the 2-m air temperatures. So if reported temperatures are below 35-36F, you better be careful--the road could be at freezing or below. If the temperature sensor on your car is below 35F, better be careful.

For the gardener, don't think that you don't have to worry about protecting frost-sensitive plants if the temperatures are above freezing. Protect when temperatures are below 35-36F.

Reminder: If you need a new calendar for 2012 please consider the Washington Weather Calendar--available at: http://www.weather-calendar.com/washington/
Buy three or more and you get free shipping.

One dollar from each calendar goes to supporting the student chapter of the American Meteorological Society!

Fog Outside, Desert Humidity Inside

2011-12-11T00:12:00.000-08:00

It it wet outside, dripping wet. Drizzle and fog. Relative humidity near 100%. The air is holding every bit of water vapor it can. And its cold outside as well...perhaps in the 30s, like most of the last few days.

But the strange thing is that inside the air is as dry as a desert, with relative humidities down into the teens or less. You walk on a rug and touch a door knob or piece of metal and ZAP...a spark! Your skin feels rough and uncomfortable from the low humidity--perhaps you get some skin cracks on your feet or hands. Your throat feels dry.

How can this be? How can the humidity outside be near 100% while inside its is more like the Mojave Desert?

Well, it all has to do with the amount of water air can hold as temperature varies.

The amount of water vapor a volume of air can contain (hold is really the wrong word) depends greatly on temperature...in fact, it increases very, very quickly (exponentially!) with temperature. Warm air can contain a LOT more water vapor than cold air. Here is a plot to show you the story:

You are stuck with degrees centigrade...this is science! The y-axis is the saturation mixing ratio--the number of grams of water vapor per kg of dry air--for saturated air as temperature varies.. At 0C there is only 4 grams of water vapor per kg of dry air, while at 20C (68F) there is 15!.

Lets say the temperature is 0C (32F) outside with a relative humidity of 100%...the air is cold and saturated...EXACTLY what we have been "enjoying" lately. Your house or apartment has a heating system that warms the air up to say 68F (20C). The interesting thing is that your house or apartment is hardly air tight and air from the outside is continuously moving inside and heated. On average there is about one complete air change per hour, more for leaky older homes, less for newer homes built tight.

Anyway, using the above chart, the 100% outside saturated air has about 4 gram of water vapor per kg of dry air. Now you bring it inside and heat the air. Inside, the air has the same amount of water vapor that is started with--4 g per kg of dry air. At 20C the saturation mixing ratio is now roughly 15 g per kg. The air now can hold MUCH more water vapor than it started with and the air is no longer saturated..not even close!

The relative humidity is defined as 100 times the amount of water vapor in a sample of air divided by the maximum about of water vapor that air can hold at that temperature.

So in this case we get RH = 100 * 4/15 = 27% Wow...that air is now very dry in the sense the relative humidity is much lower (remember, it still has the same amount of water vapor)

What happens if you heat your home to a temperature above 68F? Or if the temperature outside is colder than 32F? Or if the air outside does not start off completely saturated? The relative humidity would be much lower...and it is quite easy to get relative humidities down into the teens and single digits.

Supposedly relative humidities of 30-50% are the most healthful. Some people hate the dryness so much they put small water sprayers into their furnace or purchase humidifiers. Or use lots of creams to create a protective barrier on their skin.

Amazing Fog Pictures and Inversions

2011-12-09T13:46:00.000-08:00

Special Eclipse Forecast: I got up at 5 AM...and saw the eclipse begin...

Last night we developed a very strong inversion and a shallow fog layer that has now mainly burnt off. At daybreak many land areas around the Sound had fog, while large areas of the Sound were clear.

Here is an extraordinary picture sent to me by Tracee Geernaert at a location on Salmon Bay, looking to the north. You see those wave-like structures---reminiscent of breaking waves on a beach? Stunning. Those are examples of Kelvin-Helmholtz Instability (KHI) waves that are produced when there a very large change in wind with height over a layer of the atmosphere that is stable.

These are also called billow clouds. Here are a few more examples:

Such clouds can be associated with substantial turbulence as they roll up and break. Often quite turbulent to fly through. A few years ago I was sitting in a window seat on an aircraft and saw those clouds ahead of us. I told the person next to me that it would be a good idea to put on her seatbelt. She laughed at me. A few minutes later we hit moderate turbulence. She wasn't laughing anymore.

Some beautiful shots this morning of the sun and shallow fog from the Queen Anne and Space Needle cams:

Last night warm air moved in aloft and offshore flow increased. As result the inversion aloft really cranked up. Here is the temperature structure at 8:30 AM this morning over the Puget Sound region:

Around 30F near the surface, but in the mid-50s above 2500ft. Very strong inversion! Want to hear something amazing? The temperature right now (1 PM) at Mowich snotel site west of Mt. Rainier, at an elevation of 3150 ft, is 62F! And it is 50F at Paradise on Mt. Rainer (5500ft). Can you imagine? You could be hiking in bright sun in 60F temperature right now!

Let me end with an extraordinary shot this morning of the fog from Peter Benda's house at 1100 ft in Bellevue

High Pressure Produces Low Sea Level

2011-12-07T12:34:00.000-08:00

During roughly the past week, sea level pressure has been unusually high--including the record-breaking high pressure observed on December 1 (1043.4 hPa). Here is the pressure of the last four weeks. The first three weeks had relatively normal sea level pressures (1000-1020 mb), but the last week or so, pressures have generally ranged from roughly 1030-1035 mb. Very unusual to stay that high for so long.

We have also been observing another anomaly: the height of the water levels in the region have been unusually LOW, particularly along the Pacific coast. NOAA produces water-level predictions = (the tide tables we know so well) and these predictions are generally quite good, since we understand very well what produces tides and their periodicities. But recently the tide predictions have been greatly in error, forecasting tides that are much too high by one or two feet! Here is the predicted and observed water level at Neah Bay, provided to me by UW's Dr. Nate Mantua.

Turns out these two anomalies (high pressure and low water levels) are directly connected, with high pressure pushing water levels down.

The general term for this mechanism is the inverse barometer, and is often used to explain unusually high water levels when low pressure is over a water-covered area (see graphic)--and you may

remember that I wrote about this a few years ago when record low pressure spread over the west coast (click here for my past blog). In general, the water level should sink around 1 cm for every mb pressure increases. We have experienced about a 20 mb high-pressure anomaly, and thus one would expect water levels around 20 cm (8 inches) below normal.

However, there is something else going on here. The center of the high pressure has generally been offshore and as a result northerly winds have been persistent along the Northwest coast (see graphic from WRF model forecast):

Northerly winds put a force on the water to the south, but because of the Coriolis effect, there is an offshore component to the surface currents. Thus, surface currents are pulling water AWAY from the coast, further reducing the height of the water surface.

And it is better than that if you like low water levels. With a complete absence of storms there are no strong winds pushing water up on the coast and very weak wave action. Take a look at the wave heights along the Washington and Oregon coasts at two NWS coastal buoys for the past five days (46041 off of WA, 46050 off of Oregon). Waves progressively decreased to 4-5 ft. Good time for fishing?

We will be stuck in this pattern (high pressure, low clouds west of the Cascade crest, air pollution) for several more days, so you better get used to it. Want sun, head into the mountains or eastern WA or OR.

PS: If you want me to answer a question on-air on KPLU on Friday at 9 AM, you can leave it at this link.

Seattle's Math Secret Revealed (Revised)

2011-12-05T21:12:00.000-08:00

A few weeks ago I was sworn to secrecy by a Seattle School Board member after he/she revealed a stunning fact: one of Seattle's middle schools has had an extraordinary, if not meteoric, rise in student math performance. A middle school with very high levels of underprivileged kids--Mercer Middle School--had student math scores equal to the best in the city. And he/she had found out why: without permission from the district, the school's teachers had ditched the district's official curricula (Connected Math), a very poor "discovery" program, for the excellent, and far more traditional Saxon Math series. That school board member asked me and others to keep quiet about it, because if it got out the District administration (headed by Superintendent Susan Enfield) might well end the experiment.

(For those not familiar with discovery math, it is approach in which "direct instruction" is phased out in favor of having students "discover" math principles on their own. Lots of talking about the process of discovery, group work is stressed as is calculator usage. Exercises to encourage competency in basic algorithms are frowned on--they call it "drill and kill.")

Well, today the secret was revealed thanks to a front page Seattle Times article by Brian Rosenthal. As noted by Seattle School Director Kay Smith Blum: "They did it sort of undercover."

How good are the results at Mercer? How many ways can you say spectacular? To start, here is a graphic from the Seattle Times for the percentage of 7th Grade students passing the state math exam. In 2005, with the WASL, only 33% of the students passed the exam, compared to 47.3% of the students from the entire district. Mercer Middle School students were lagging behind. In 2011 on the state MSP exam, students at Mercer WERE DOING BETTER than the district average. (NOTE: you can't compare the two years directly--different exams!!, but you can compare differences within the district)

But let me show you some graphics based on this year's State MSP math exam (thanks to Paul Dunham for providing the data). These plots show you the performance of several middle schools, with the schools in order of percentage of students on free and reduced lunch. The ones on the left are schools with rich demographics and on the right, schools with poorer students. Mercer is the second from the right in all of them. In general you would expect the richer, more privileged students to do better for the obvious reasons.

First lets compare the performance of the various schools for blacks, hispanics, and asians. Mercer is the best for blacks and hispanics, and a close second for asians.

Or how about low income and limited-English kids in 6th grade? Mercer is the best!

Seventh Grade? Mercer is the best for low income and second best for limited English.

The district has had a huge problem of minority and underprivileged kids doing much worse in math than the rest of the district. Mercer has essentially solved the problem by going against the district's chosen curriculum.

Here is more proof it is the changed math curriculum that has made the difference. Take a look at the 8th grade math performance at Mercer compared to other Seattle middle schools:

Mercer's performance has worsened compared to the others. There is a reason. According to a teacher from Mercer who left a comment on this blog, Mercer does not use Saxon in the 8th grade..only 6th and 7th, and only for struggling students. Thus, student performance starts to decline relative to other schools in 8th grade. This really is unfortunate. It is like finding someone that is drowning. You throw them a life preserver and they think they are saved. Then you take the life preserver away and let them flail in the water again. Just not right.

This underground experiment is not the only in the city. Two schools in the city: Schmitz Park and North Beach Elementary (see PS below) have gotten permission for limited periods to use non-discovery, more traditional math books. The result: HUGE increases in learning and performance of their students. For example, Schmitz Park Elementary got permission to try Singapore Math textbooks in 2007 (traditional direct instruction). Its students’ math scores soared: in 2010 the 5^th graders had the third highest passing rate in the state on the state test, even though the school has no gifted magnet program.

In some of my previous blogs, I have also described what has happened in other districts when Discovery Math has been replaced by excellent curricula such as Saxon or Singapore. Scores have jumped substantially in math.

Now the district administration knows about this. In fact, Superintendent Susan Enfield was asked by the Seattle Times whether she knew about the phenomenal results at Schmitz Park and North Beach (you can watch it below). She did and her basic answer was that they have a core (Discovery) curriculum and the district is going to stick to it. Just amazing. Stunning results do not matter to her at all. In fact, Dr. Enfield is a proponent of Discovery math and pushed the Discovering Math high school series when she was curriculum head.

Click to see Enfield Interview by Seattle Times

The bottom line of all this: It is now absolutely clear from a huge amount of evidence that discovery math programs don't work and that they particularly hurt minorities, the disadvantaged, and those with weaker English skills. They also hurt the top demographics as well. Seattle has extraordinarily poor discovery math at all levels (Everyday Math-elementary, Connected Math-middle schools, Discovering Math-high schools). Suburban districts like Shoreline and Bellevue have dropped discovery math after seeing it undermine student performance. Enfield, is clearly not interested in replacing the current curricula and it is up to parents and the school board to force this issue. (As noted in my earlier blogs, discovery math is like a religion to many in the educational community, particularly schools of education. The latest fad in a long line of failed fads). The current curricula are crippling the futures of Seattle's kids. You would think the district would be designing experiments in many of its schools to see which method of instruction works best and then to move to the superior method... it is not. Imagine, testing various curricula with classes of similar demographics and learning what works and doesn't. Use this approach to steadily improve instruction and student performance. You would think that any rational and concerned district would try such a scientific approach. Not Seattle Public Schools.

If you are a Seattle parent let school board members know what you think, if you are a business, tell the district administration that policies must change. Susan Enfield is now only interim and the school board will vote in the next few weeks whether to give her a permanent contract--which would be a disaster for our kids. It is time for a change from her failed policies (and disasters like the firing a popular Ingraham HS principal), and hopefully with the assistance of two new school board members, the district can finally follow logic and the evidence of student performance, and the not the ideological leanings of several in the school district administration. Superintendent Enfield is so confident of her position she has told the board that if they dared to open the selection processes to consider others, she would remove herself from consideration. There is a word for such an attitude, but it doesn't belong in a family oriented blog like this one.

PS: Here is a comment I received that is so relevant and important, I am posting it here:

I was fortunate to be the principal who brought Saxon Math (after the teachers voted for its use)to Seattle’s North Beach Elementary in 2001. I had used it as a teacher and principal on the Spokane Indian Reservation in the early 1990s and we saw great success with Saxon’s traditional material. The Seattle district staff were stressed by my choice of Saxon because it is used, they declared, primarily with lower performing (high risk) students and North Beach was 80% upper middle class. But the supt at the time stressed site-based decision making, so we took advantage of that policy. Saxon Publishers allowed us to be a pilot site with free materials for K-2 the first year.
The next year, our parents and teachers were so supportive of Saxon’s effects on our students, the PTA raised money to buy materials for grades K-5. Saxon Publishers also gave us some special rates. Within 4 years, these “white” kids with their 66% math passing rate in 2000, had achieved 91% passing (for 4th graders at the time). We had proved that curriculum makes a HUGE difference for every economic group of students.
After I left North Beach in 2004, there were concerted efforts by district staff to get rid of Saxon Math. You see, results for the children are rarely the issue in math curriculum choices by urban districts’ decision makers. It’s about being a “team player” with the adults in charge, who follow a particular ideological path of reform materials for creating equity in classrooms, not excellence in mathematics.
The North Beach math scores have dropped precipitously as some assigned principals have fought the parents’ and teachers’ use of Saxon.
By the way, even if Saxon were for only the lower performing kids, that means it should be used by 50% of the nation’s students and 70% of those in urban districts.

The Irony of Wintertime High Pressure

2011-12-03T09:47:00.000-08:00

High pressure is good, right? Sunny skies, light winds, and dry conditions? A nice break from stormy, wet conditions? Not necessarily true here over the western lowlands during cool season. For us, high pressure often brings something I personally dislike more than storms---endless low clouds. And often air pollution as well.

It is Saturday morning and here is the latest visible satellite picture. Low clouds over the Willamette Valley and western Washington lowlands. There are clear skies over the mountains, along much of the coast, and yes over those fortunate folks in Sequim and Victoria. Some higher clouds are found over eastern Washington from a weak system moving southward out of Canada.

As shown by this morning's surface pressure chart. high pressure dominates our region, with the center of the high pressure offshore. No storms, no rain, no snow. The pressure gradients over us are weak and the winds are light. It appears that we are going to be stuck in this pattern for the next week. Lucky us.

The problem is that in the Northwest, high pressure around during the winter is a low cloud production machine. First, with a high over us or nearby the winds are light, since the large pressure changes (gradients) are at the periphery of highs. Less winds means less turbulent mixing of air in the vertical. Highs generally bring sinking air in the troposphere and thus lack of middle and higher layer clouds. Lack of clouds means the earth can effectively radiate infrared radiation to space and thus cool the surface. The cooling surface cools the very lowest portions of the atmosphere. Air can cool to saturation and give you fog and low clouds.

Saturday morning in Seattle. Mt. Rainier is straight ahead. See it?

And having cool air near the surface and warmer air above leads to an inversion--temperatures increasing with height. And inversions cause the atmosphere to become very stable, with little mixing in the vertical (think of oil above water). No mixing means you can't bring the warmer air aloft down to the surface...and one stays cool and murky. Here are the latest temperatures at Seattle--you can see the inversion from 200 to 500 meters above the surface (immediately above the surface there is an issue of a different temperature sensor)

And did I mention that the very long nights this time of the year gives the surface a lot of time to cool and the weak sun hardly produces enough warming to heat the surface and mix this out? The same weather pattern in the summer would be no problem...we would have sun after perhaps some morning clouds.

And it gets worse. Since we have had rain for a while the surface is moist, with lots of water to give to the atmosphere, and with high pressure offshore, moisture streams in at low levels off the ocean. And once in place fog and low clouds cool at the top (infrared cooling to space) and tend to reinforce themselves. Diabolical.

Now today and tomorrow, the inversion will be weak and shallow enough for there to be a good chance it will mix out a bit this afternoon and give us some sun. Good time to rake leaves or take a walk. But as we get into next week, we will probably experience days in which we stay in the murk all day. The good news is that you can get out of this by going up...head to the mountains or even a high park--such as Cougar Mountain regional park. Or take a walk up Tiger Mountain (top 2500ft). The worst place to be is the southern Sound lowlands.

Finally, a major issue with such situations is air quality. Inversions and light winds bring deteriorating conditions and in fact the Puget Sound Clean Air Agency has a burn ban going on right now. Just to prove to you that air quality is declining, here are some plots from two local reporting stations. We are now seeing moderate AQ conditions and it won't be long before we are in unhealthy ones.

Anyway, it helps to know what is going on and that escape is always possible with a short drive. It gives one a sense of control.

History is Made: Highest Pressure in Sea-Tac History!

2011-12-01T12:18:00.000-08:00

We are living through historic weather. UW's Neal Johnson ran the numbers and found that the sea level pressure at Seattle-Tacoma Airport today was the highest since record keeping began there in 1948. Here are the top pressures since 1948, starting with the highest pressure first.

2011 12 01 08 1043.4

2011 12 01 07 1043.3

2011 12 01 09 1043.2

2011 12 01 10 1043.2

2011 12 01 11 1043.1

1949 01 28 16 1043.0

1949 01 28 17 1043.0

1949 01 28 14 1042.7

2011 12 01 06 1042.6

1949 01 28 13 1042.3

1949 01 28 15 1042.3

1949 01 28 18 1042.3

1949 01 28 19 1042.3

1957 01 16 10 1042.3

1957 01 16 11 1042.3

Last night at midnight Sea-Tac hit 1043.4 hPa, smashing the old record of 1043.0 hPa.

According to the Weather Underground site the highest pressure in Seattle occurred on 12/3/1921 (1043.90 hPa), but that was at a very different location (downtown Seattle, not the airport) and thus not a fair comparison.

I hope someone contacts Ripley's Believe It or Not.

Highest Pressure in Decades Over The Northwest?

2011-11-30T22:14:00.000-08:00

Do you feel the pressure? Is it like the weight of the world is on your shoulders? There may be a reason: right now we are experiencing some of the highest atmospheric pressures in years and probably decades.

Take a look at the National Weather Service sea level pressure analysis at 7 PM (below).

A very strong high pressure area is centered over the Northwest and southwest Canada, with pressures greater than 1040 hPa over much of the region and a 1046 hPa center over southern BC. 1046 hPa is equivalent to 30.89 inches of mercury. Folks, this is REALLY high sea level pressure. At Sea-Tac the 9 pm pressure was 1042.6 hPa--and it is still going up! There has been a huge pressure rise over the past 24h--roughly 20 hPa. The highest SLP I see at 9 PM is 1045.2 hPa at Lytton BC (elev 751 ft).

From experience I know these pressures are very unusual, but lets check the UW pressure archives. Here are the hourly pressures at Sea-Tac airport since 1996. Looks to me like the pressure last hour (9PM Wednesday is the final plotted red dot) was the highest during the entire record shown here (I confirmed by looking at the numbers). So the highest pressure in 15 years! That is impressive.

And the pressure is still going up! The Portland International Airport has recorded a maximum barometric pressure reading of 30.76" (4:53am observation) which is tied for the second highest reading since records began at the airport in 1940 (thanks to Steve Pierce for this information). The bottom line is that we are experiencing truly unusual pressure right now...I wonder what this does to people with arthritis and sensitive joints.

This push of high pressure over the Northwest is creating huge pressure gradients over the southwest U.S. Here is the latest model prediction for tomorrow morning. High pressure over us and a big pressure differences over Colorado, Utah, Nevada, California, and the offshore waters.

Very strong winds will be the result of these big pressure gradients, including gusts hitting 50-80 mph in places. In fact, it has already started. Take a look at the latest wind reports of greater than 45 mph over the western U.S.---quite a few of them.

And here are some recent reports from the National Weather Service office near Los Angeles. Gusts as high as 69 mph so far.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE OXNARD CA
802 PM PST WED NOV 30 2011

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..

0557 PM NON-TSTM WND GST 1 NW SANTA CLARITA 34.42N 118.53W
11/30/2011 M67 MPH LOS ANGELES CA MESONET

67 MPH GUST AT SAUGUS RAWS LOCATED 1450 FT

0555 PM NON-TSTM WND GST 5 N SAN FERNANDO 34.36N 118.42W
11/30/2011 M64 MPH LOS ANGELES CA MESONET

64 MPH HOUR GUST AT CAMP NINE RAWS LOCATED AT 4000 FT

0753 PM NON-TSTM WND GST 8 ESE CASTAIC LAKE 34.60N 118.58W
11/30/2011 M69 MPH LOS ANGELES CA MESONET

69 MPH GUST AT WARM SPRINGS RAWS LOCATED AT 4930 FT

High pressure will bring us dry conditions and some sun...but air quality may decline.

Climatologically, The Worst of Winter is Over!

2011-11-28T21:26:00.000-08:00

Yes, you read that right.

The last week or two of November is climatologically the worst period of the year by many measures. For example, consider the average precipitation per day at Sea-Tac Airport (below). It peaks in last November and most of December is a drier.

Or how about extreme daily precipitation at the same location?

Big peaks in November and a radical reduction in extreme precipitation in December.

Just like clockwork there is going to be a major break in the coming up this week, but first we have to get through one more storm. A low center and accompanying clouds and precipitation is moving towards us from the northwest and should bring precipitation to the region late tomorrow and Wednesday AM. You can see it off our coast in this satellite image:

This system should be unremarkable. After that a very strong ridge will build northward into the eastern Pacific and will remain in place for at least a week. You heard me...a week.

Like Wednesday morning

Thursday morning

Friday morning

Saturday morning

You get the idea. And we will have lots of sun...and some fog in the AM. The biggest threat to your life and safety will be ice on the roadways. Will we have another big storm...of course we will. And a good chance of some lowland snow. But ON AVERAGE things typically improve as we move out of late November into December.

The National Weather Service has this regime going into next week...here is their latest 6-10 day precipitation forecast: below normal in the West.

This looks like a good time for local meteorologists to go on vacation. Or to rake some leaves.

PS: I know "official" winter starts on December 22 and ends in March. The point is that calendar winter is really quite different than meteorological winter in many parts of the country...and we are a good example of that. Around here the end of February could really be considered the end of winter....sun is much stronger, far less weather systems, chance of flooding goes to near zero, etc. And the grass starts growing again on the west side of the Cascades. When I have to mow my lawn, winter is over..period.

Why is Northwest Washington So Windy?

2011-11-26T22:50:00.000-08:00

It seems like it occurs during nearly every storm. Before a front or low center hits our region, one area gets winds first--and they are often very strong and from the southeast . We are talking gusts about 50 mph and higher in the stronger events. And then after the storm moves by, they get hit by powerful winds from west.

What is this benighted region, one in which Seattle TV stations often stage their camera crews for dramatic wind shots?

The answer: Northwest Washington...the region extending north and west of Everett, over northern Whidbey Island, to the San Juans and down to the NE tip of the Olympic Peninsula.

Why is this region so windblown? And why only certain directions? Why can the winds be blowing at gale force there, while Seattle is practically calm? I will try to explain in this blog. We have had a number of major NW Washington wind events this month and another will hit tomorrow (Sunday, 11/27).

Northwest Wind Land

I got my first personal taste of the NW Washington winds in the 80s while I spent the night at Rosario Resort on Orcas Island. The winds came up quickly that night and they were roaring! Just heaven.

A mild event is going on right now (Saturday, 9 PM). Here are the winds:

Calm in Seattle and Port Angeles. Very light winds at Sequim and Victoria. 30 knot sustained winds at Smith Island and northern Whidbey Island. Gust over 40 mph. These radical differences in weather over short distances are why we love Northwest weather!

Sunday morning things will really be blowing: here is the lasted WRF model forecast of sustained winds at 4 AM. Sustained winds of 40 kts (46 mph)...with higher gusts, of course.

So why the strong winds? One reason is the extensive amount of water in the area and winds blow much stronger over water because it is aerodynamically smooth. But there is something else....the OLYMPICS!. The mountains distort the local pressure field, with pressure being increased on the windward side and decreasing on the leeward side. The winds in these situations are almost always from the south...thus there is high pressure on the southern flanks of the Olympics (rising air causing cooling and cool air is more dense and thus results in higher pressure) and lower pressure (leeside trough) on the northern side where air sinks and warms by compression. Here is a graphic of the situation at the same time as the previous figure...the lines are isobars (lines of constant pressure) and the wind barbs are shown too. See the distortion of the isobars by the Olympics? Nice lee low by Port Angeles and Sequim. Do you see how the distortion caused the isobars to bunch up from roughly Everett to Whidbey Island? Such a large change in pressure is called a large pressure gradient. That causes the winds to accelerate greatly as the air moves from higher to lower pressure....and is the essential cause of the strong winds observed tonight and on Sunday....and many other times!

You need good southerly flow approaching the Olympics to get this effect...and such southerlies often precede a strong front or accompany an approaching low that is headed to the north of us. In fact, when a low goes north there is a background south to north pressure difference that can really add to the strength of the southerlies forced by the Olympic effect noted above. Here is a larger scale view of the pressure situation tomorrow at 4 AM... a strong front IS approaching.

Just to show how windy Smith Island (just west of Whidbey Is) can get, take a look at he recent max gusts there. Lots of 35-40 kt gusts the last day and nearly 60 kts on the 24th.

But wait until tomorrow morning! You can check the winds yourself at this site:

http://www.ndbc.noaa.gov/maps/NW_Straits_Sound.shtml

Weather Gifts

2011-11-25T08:38:00.000-08:00

Today is Black Friday when many people are thinking about getting that perfect gift for friends, loved ones, and even for yourself!

Why hit the malls for a sweater or electronic luxury when you can get a weather-related present?
A weather gift is great for that budding young meteorologist or to determine the weather at one's home or business. To connect in an intimate way with the environment around you. I have gotten a lot of questions over the years about the best weather stations or weather instruments--and I will answer some of them here. You don't have to spend a lot of money on weather gear to get a good start, and remember many of the founding fathers of our country (Washington, Jefferson, and Franklin) were weather enthusiasts and took their own observations for years! To quote Benjamin Franklin:

Some are weatherwise; some are otherwise.

My own career in meteorology began with a Lionel weather station my parents gave me as a nine-year old.

Books and Calendars

It is always good to read up on the subject. Now, of course I am biased and recommend my own book: The Weather of the Pacific Northwest, available in local bookstores and online (Amazon, Barnes and Noble, etc). This book was written for layman and has lots of color pictures and graphics and is reasonably priced ($20-30).

You want a general introduction to weather? A good book, although pricy, is the textbook I used in Atmospheric Sciences 101: Essentials of Meteorology by Donald Ahrens. The new books are an absolute rip-off (like $140!) but you can get used books for $20-30. (Some day I will blog about the corrupt textbook publishing industry). Get an old edition...essentially the same.

AMS Weather Books also has an accessible introduction to weather and only costs around $25.00: The Ultimate Guide to America's Weather.

A weather calendar is also a nice gift, particularly one directed towards your area, with information about daily climatology and records. Well, the Washington Weather Calendar is available for only $14 and has local weather records and average conditions for each day...plus, $1 of each calendar helps support the UW Student Chapter of the American Meteorological Society.

Cloud Charts

Want to learn the clouds and get a nice poster at the same time? Get a large cloud chart! Perhaps the best was created by UW's Art Rangno and is available at many outlets and online for only about $7.00!

Inexpensive Weather Instruments

Want to start observing the weather but your budget is limited? Rain gauges are both fun, useful, and relatively inexpensive. You can pick up garden rain gauges for $10-15 at garden stores or Lowes/Home Depot, or you get a truly high-quality gauge for around $30. A good one is used in the Cocorah national rain gauge network and can be order online at http://www.ambientweather.com/strgloteprra.html (see below)

Remote temperature sensors are also reasonably prices ($20-30) and can be purchased at local stores (Bartell, Fred Meyer) or online.

These units are relatively accurate and give you high and low temperatures.

Complete Weather Stations

For real enthusiasts who have more available funds, a complete weather station might be what you want. Such units measure temperature, humidity, pressure, precipitation, and wind speed and direction--and for more money you can get even capabilities (e.g., solar radiation). The quality of these units range from modest to professional quality and prices extend from just over one hundred dollars to a thousand dollars and more. Many allow you to interface your weather statoin to a computer for display and archival, as well as putting your data on the web in real time.

Based on our experience at the UW interacting with many networks and installations, probably the best deal (quality and price combined) is for the Davis Vantage Pro systems. The Vantage Pro 2 costs about $500:

Cheaper unit, but not as good, are available online, Costco, and other outlets. A good list of them is available at: http://www.weathershack.com/home-weather-stations.html

Few activities are as enjoyable as understanding and observing the weather, and these gifts give you a good start at it.

An Extraordinary Storm

2011-11-22T20:53:00.000-08:00

This is turning out to be a major winter storm, with serious rainfall, flooding, and winds. And it is not over yet...some of the biggest action is yet to come. This event is also spotlighting a lot of new technology: coastal radars, super-hi resolution modeling, and others.

A lot of the rain is still yet to come, but consider the rainfall of the last 48h as shown in our RainWatch site:

Over five inches near the Hood Canal area and 2-3 inches extending eastward to the Cascades where precipitation picks up again. You can add at least another inch or two to this before the event is over. However, the real precipitation hot spot is to the south over the southern Cascades and northern Oregon coastal mountains. Here is the latest storm precipitation total from the Portland radar (not as well calibrated as the above image) at 8:23 PM Tuesday (roughly past 48h):

Some values in the southern Cascades reaching 8 inches according to the radar. Several raingauges there have reported 5-6 inches over the past 24 hr.

The National Weather Service is now predicting flooding on several rivers, some with moderate flooding, as seen by this figure from their website:

A particular threat is for the Chehalis River, where moderate flooding is predicted--although there is lots of rivers flooding over southwest WA and NE Oregon. Even the Snoqualmie is getting to bankfull. The Skokomish always floods...but that is another story.

A few of you have commented that this seems too cool for a pineapple express event and you are right. This is not a classic pineapple express event in which warm, moist air feeds up from deep in the tropics and subtropics. Temperatures are far more moderate and a look at the cloud shows that moisture is streaming from the southwest but not down to the vicinity of Hawaii (see picture). In fact, some of the moisture can be traced back far, far to the west--perhaps we should call it the Sushi Express.

But the other story here is wind and we have had some amazing winds...including 97 mph at Mt. Hebo in the Oregon coastal mountains, 70 mph at Bellingham, 70-85 mph on the Cascade crests, and 60-70 mph gusts all along the Washington and Oregon coasts. But the big action is about to happen over the Oregon coast, where the WRF high-resolution model is going for sustained 50 kt winds tonight, with higher gusts (see graphic). If you are on the Oregon coast, you better get some batteries.


Forecast winds at 1 AM Wednesday

The new coastal radar has been a real boon to local meteorologists during this event...telling us what is coming and how long the rain will continue. Here is a great shot showing a front (narrow line with red embedded) approach the coast last night...a front that represented the temporary end of rain this morning:

The models have really been good--getting the timing and major features correct.

And did I mention the over a foot of snow in the mountain passes today and more over the North Cascades. With high to extreme avalanche danger as all this wet heavy snow falls on the light snow with embedded weak layers. This is really a good time to be a local weather lover...more action than one can keep track of.

Major Storm: Heavy Rain, Flooding and Very Strong Winds Along the Coast

2011-11-21T10:04:00.000-08:00

A VERY serious storm is going to hit the Northwest during the next two days--one that will cause flooding and coastal wind damage. And the urban areas are doing to experience a deluge.

Here is the forecast precipitation over the next 48h over the region and over western Washington.The Olympics, the north Cascades, and the mountains of southwest Washington and NW Oregon are going to get hammered with 5-10 inches of rain (reds). Even Seattle will get nearly 4-5 inches if this forecast verifies.

Folks, this will be a major event.

There is a serious threat of flooding on a number of rivers. The Skokomish is a given. It looks like there will be flooding of the Chehalis...and that means those near the river should prepare. The NWS River Forecast Center is going for a major flood at points along the Chehalis....here is an example:

And there are others that I won't list now.

The other threat of this event is wind--HUGE winds along the Washington and Oregon coasts (worst along the Oregon coast). Take a look at this forecast of sustained winds for 1 AM on Wednesday morning. Sustained winds of 50 kts with gusts heading to 70-80.

The Washington coast will get the strong winds earlier...tonight...see below:

Regarding snow, the models are putting a few feet over the north Cascade...and far less to the south where the freezing level will be relatively high. An interesting aspect of this case is that it is NOT a pineapple express event with a moisture plume extending from just north of Hawaii.

Anyway, I believe a major storm event is about to unfold...and it will be fascinating to use the new Langley Hill radar.

Northwest Flood Myths and A Major Flood Threat

2011-11-20T10:28:00.000-08:00

As we gird ourselves for a period of heavy precipitation and probable flooding on some local rivers, it is probably a good time to talk about some "myths" regarding Northwest flooding events. Some of these I have discussed previously in this blog, but recently I read a very nice summary of these misconceptions prepared for the USGS by Joseph Jones. Here are a few:

MYTH: A "100-year" flood only happens every 100 years on average.
FACT: a "100-year" flood happens about every 4.5 years on rivers draining into Puget Sound

How many times have you heard on the news about some locale in the region having a "100-year" flood? A few I bet. When there is more than one over a relatively short period (5-10 years) some people suggest something is wrong with the way meteorologists/hydrologists decide such things. Others suggest that this is PROOF that global warming causing more extreme precipitation (I have a collection of such statements by activist groups and NGOs s that I will spare you right now). How many 100-year floods have we had lately? January 2009 for the central WA Cascades, December 2007 over southwest Washington and Northwest Oregon, October 2003 over Northwest WA, February 2006 for northern Oregon and southwest WA. And there are more.

Believe it or not, having frequent "100-year" floods over the region is just what one would expect. Let me explain. When we use the term "100-year flood" we mean a 100-year recurrence interval...a flood we would expect to be observed once in 100 years at some location. Or to put it another way, a flood with a 1% chance of being exceeded at a point in a given year.

Now the first thing to consider is that if there is a 1% chance of something happening in a year, it is possible for two events happening two years in a row. Just like getting two heads in a row when an unbiased coin is flipped. But there is something else that is more important in this case. The term 100-year flood is talking about the chances of getting a flood at some location. As the distance between points increase, the flooding at the points becomes less and less correlated. You can get a flood at one location and not another. Think of it this way....it is like flipping coins at more than one location and so the chances of getting two heads in a row are increased. Thus, if one considers a region, the chances of getting a 100-year flood somewhere in the region is greatly enhanced over a single point. A careful evaluation of the probabilities (e.g., Troutman and Karlinger 2003, Water Resources Research) reveals that for the rivers draining into Puget Sound one would expect a 100-year storm every 4.5 years! If you widened your viewpoint to the all of western Oregon and Washington, the chances would even be better.

So if we have an 100-year flood every year or so around the region..that is exactly what one would expect and you don't need climate change to get it.

MYTH: Rain-on-snow events, where warm rain falls on and melts a lot of snow, is a major cause of severe flooding. In other words, melting snow is a critical component of major floods.

FACT: Rainfall intensity and duration are the keys elements for all major local floods. Melting snow might contribute in a minor way, but is not required.

If one analyzes the major floods in western Washington, all have been associated with extreme precipitation that could explain the vast majority of the flooding (reference: hydrological expert Professor Dennis Lettenmaier of the UW, chief US Army Corps of Engineer meteorologist in Seattle--Harry Schick). Several major floods early in the season occurred when there was little if any snow to melt--just as October 20, 2003.

This Week's Situation

There is a very serious heavy rain and flooding event setting up this week. Originally it looked like the Olympics would be be in the center of the plume of moisture, but the latest model runs suggest the heaviest precipitation could be over southwest WA, northwest Oregon, and the southern WA Cascades. Even the Puget Sound region will get a lot of rain and it would be worse for Portland. Here is the 48-h total precipitation ending 4 PM Wednesday. The reds are 5-10 inches--and most of this occurs over 24h (see second graphic for 24-h precipitation ending 4 AM on Wednesday).

Here is a blow-up 48h rainfall over Washington--Portland is going to get hit hard if this is true with some isolated areas of over 10 inches of precipitation. It is going to fascinating (and scary) to watch this unfold with the new coastal Doppler radar. This is the kind of situation it was installed to help with.

My Lost Dog Situation
Leah, our black and white female cockapoo, is still on the loose in Mountlake Terrace...we have had some sightings and one person even gave her a hamburger before she bolted. Our biggest problem is that the City of Mountlake Terrace is removing our signs, even ones on private property. Last sighting was near the Moose Casino off of SW 220th. If you live in that area, please let us know if you see her.

Snow Update

2011-11-18T20:23:00.000-08:00

It is is looking increasingly unlikely there will be any significant snow over the lowlands tonight north and west of Olympia. Just a few scattered snow showers, particularly over higher hills and in a dying convergence zone near Everett and extending east. The latest model runs show far less precipitation and a much more amorphous low center (see graphic below). Less cold air moving in...in fact, the freezing level has gone up to

Forecast 4 AM sea level pressure and temperatures

2000 ft, which implies a roughly 1000 ft snow-level. Our wonderful new Langley Hill radar show some strong showers coming to the coast right now...but very little significant precipitation behind it (see below):

8:20 PM radar

The ensemble forecasting system and probcast concur on predicting dry conditions for the Sound and northwards, but some light snow showers to the southeast of the Sound. Perhaps some light snow over the NE slopes of the Olympics and eastern Vancouver Is. Here is the predicted 24-h snowfall ending 4 PM Saturday. There could be some light snow in the Centralia/Chehalis area and over SW Washington. Of course, with it being cold enough for snow tomorrow morning...so we will need to be attentive for the forecast going wrong...

Mixed clouds and sun tomorrow after the late morning, but quite cool (lower 40s should be it). Heavy rain still on tap for Tuesday. This is a serious threat for those living near the Olympic Mountains...and will be the first major event observable with the new Langley Hill radar.

Lowland Snow?

2011-11-17T21:46:00.000-08:00

Snow Update on KPLU (88.5 in the Puget Sound area) at 9 AM Friday--Available on the Their Website

Yes, there has been lots of talk about lowland snow--enough to give local mayors insomnia. And some local TV stations are claiming that they have reports of snow on a few local hills. I bet Jim Forman of KING TV is getting his famous parka dry cleaned or something.

Right now the air over is cold, but really too warm for significant lowland snow. Here is the latest temperatures aloft from the UW SnowWatch system, which makes use of aircraft observations (ACARS) coming into Seattle. The blue dots are temperatures from the profiler system at Sand Point, which are not as dependable. The freezing level is around 1800 ft, which generally means the snow level is 800 ft, 1000 ft lower. Snow melts out in that 1000 ft. A really heavy shower could drive the snow level a bit lower.

Some showers are moving through right now, bringing rain to the lowlands and more snow to the mountains. Lots of snow. (see radar below). It is a bit colder in the NW part of the

state and there has even been some NE flow coming into Bellingham where they have had a bit of freezing rain reported. Seattle and the north Sound have been rainshadowed for the last few hours...so nothing fun there and the worst of the showers are moving to the south. The Langley Hill radar shows things quieting down offshore.

Tomorrow will be cool and dull, with a few chilly showers and not much more over the lowlands. Decent for the Occupy Seattle protestors and for the helicopters that are following them aloft. The fun waits until later Friday when a low center moves towards the SW corner of the state (see graphic at 7 PM Friday). Now normally I would be getting REAL excited when such a situation, which has a lot in common with major snow events in western WA, but there are problems for lowland snow lovers. The temperatures are still marginal at this point and the air to the north is not super cold. There is some leakage of colder air through Bellingham at this point though. The big problem is a lack of precipitation, with the upper level support (producing strong upward motion and precipitation) being weak.

Here is the three hour precipitation for the three hours ending at 7 PM Friday. Pretty sad.

There is simply too little "juice" for this system. Here is the 24h snow predictions for the period ending 4 PM on Saturday. Some folks will get snow: the southern Cascades and the southern part of eastern Washington will get a nice white blanket and the northeasterly flow coming out of the Fraser valley will move southwestward and slam into the Olympics giving some snow to the foothills and the southern suburbs of Sequim and Port Angeles. And some odd snow showers here and there.

But now the warning and why we need to stay alert. As the low goes by the temps will cool enough for snow over most of the lowlands. If the precipitation is heavier than forecast there could be considerably more snow over sections western WA.

And another warning...the models have been consistently suggesting a strong pineapple express with very heavy rain in the mountains Tuesday/Wed. of next week. This will really mess up the snow at many of ski areas (the lower ones).

PS: Apologies to engaged retirees. In my previous analysis of the School Board race I speculated why the early voters supported the incumbents and suggested that non-engaged retirees might have been to partly to blame. There are certainly many highly engaged retirees who supported change in the District. Sorry.

Snow, Wind, and Progess in Seattle

2011-11-15T21:01:00.000-08:00

It is a funny thing about the weather...when things get interesting EVERYTHING seems to happen at once. Or let me put it this way. Sometimes there are ingredients for a major explosion laying around...the fuse, the matches, the explosives. The question is whether they will all come together to produce the big bang. Explosion or not, a lot is going to happen during the next few days!

The last few days have been colder than normal (see figure) and ironically the first two weeks of November has been considerably drier than normal (by about two inches here in Seattle). That will change.

Red lines show average high, blue lines average low

You are about to experience a weather roller coaster. Tomorrow, a strong warm front will move up the coast (see surface chart) and before it passes powerful southeasterly winds (sustained 30-50 mph with gust far higher) will strike the Vancouver Island coast. (see wind graphic) and strong southeasterlies will strike the waterways of NW Washington (30-40 mph gusts).

This warm front and its associated low will bring heavy precipitation to the region...rain below 2000 ft and snow...lots of it.. in the mountains. Here are the predictions for snowfall during the the next two 24h periods:

We are talking about the potential for several feet in the mountains and significant snow on the eastern slopes of the Cascades and northeast Washington (produced by easterly upslope flow as the front and low approach). Travel in the passes could be problematic...especially the higher ones. Prediction: some of the ski areas will be open for Thanksgiving.

But then we get to the fun part. The warm front moves through, followed by a cold front. Cooler air moves in. The low center moves southward to the southwest top of Washington and cool air is drawn in through the Fraser River Valley. Some of it strikes the Olympics around Sequim, producing some light snow. (see figure).

This is getting close to the western Washington snow pattern except for two important issues: there is little or no precipitation by this point due to lack of upper level support...maybe a few showers--yes even snow showers. And the air is not quite cold enough to guarantee snow. But remember what I said about explosives....a lot of the ingredients are in the vicinity, if the evolution is a bit different than well...it could get interesting.

Seattle School Board Victories

The Seattle School board race faced incumbents, who supported very poor math textbooks and who were extraordinarily uncurious about the illicit and wasteful activities in the district, against some excellent challengers. Two days ago, one of the challengers--Marty McLaren--was declared the victor by her opponent. Today, Sharon Peaslee moved ahead of incumbent Peter Maier and it is clear that she will win. This is an extraordinary victory for Seattle's kids and the city in general. A game changer. Both Sharon and Marty support world-class math instruction that will allow our kids to be competitive with student in Singapore, Finland, and other top education countries. They both prize the opinion of parents and the community--opinions the incumbents have ignored. Sharon and Marty are not in "blame the teacher" mode that is so popular among the incumbents and their monied allies from the eastside. They will ask questions and will want to take a careful look at the "books". These new school board members, plus continuing members that have shown a willingness to listen to the community, can promote a new direction for Seattle Schools, and I trust a quick exit for the current mediocre Acting Superintendent Susan Enfield, who has made one serious error after another. The Seattle Times has played a very negative role in this race--supporting the incumbents because they were "professional" and because they knew where the problems were (since they caused them!). The ST even had an editorial complaining when one of the challengers won and blamed it on "the unions." and crowed that Peter Maier handily beat his challenger. I have been embarrassed for the ST and hope they rethink their shallow and uninformed editorial approach to the Seattle Schools--the community deserves better, much better.

PS: It is fascinating the difference between the early and later voters in this race. Later voters broke overwhelming for the challengers. Why? The last few weeks brought headline and headline describing illegal and ill-considered actions in the district. The challengers worked very hard to get their message across. And perhaps the early voters were retired or disengaged folks that follow the recommendations of the ST (a bad idea!), while many of the later voters were busy parents who knew what REALLY was happening in the district.

Sharon Peaslee

Marty McLaren

High Winds Hit the Eastern Cascade Slopes

2011-11-13T21:00:00.000-08:00

The big weather action today was on the eastern slopes of the Cascades, where winds were gusting nearly to 100 mph at some locations-- 96 mph at Mission Ridge. Here are the winds at 7 pm and 7 AM, with the red numbers giving you the gusts:

7 AM

7 PM

The winds were very variable and intermittent...some places got hit by strong gusts for a while and later experienced light winds. Here are the winds today at a high (6730 ft) east-slope location--Mission Ridge:

Some mighty good windchill up there! In contrast, winds at Ellensburg were only gusting into the 30s (knots)

Now to understand these winds one must begin by noting we have had a VERY powerful jetstream over the Pacific that has headed right into us from the northwest.
Here is the upper level chart at 300 hPa (around 31,000 ft) at 4 PM Sunday.. Some winds are well over 150 knots, with some reaching 190 kt (219 mph!!). Don't try to fly to Asia...it will take forever.

Winds indicate by dashed lines and barbs.

These strong winds have interacted with the Cascades. First, air approaching the mountains rise, cool, becomes more dense and causes a windward high pressure area. As air descends, it warms, becomes less dense and produces a lee trough. Air accelerates as it goes from high to low pressure. And such a pressure distribution was evident across the Cascades today (see map below at 10 AM). Here is the proof.

And the interaction of the strong flow with the mountains can produce mountain waves that can bring down the momentum from aloft and enhance wind speed. Here is an east-west vertical cross section across the Cascade today and you can see this effect (shading indicates wind speeds--dark red is strong, and air flow tends to follow the solid lines):

Lets take a look at the wind gust prediction at the surface (really 10 meters) from the high resolution WRF model today at 4 PM. The first is from the 4-km grid spacing domain and the second is from our ultra-resolution 4/3 km domain. Lots of gusts over 50 kts in the high-resolution domain.

Hate to say it...but there will be plenty more of this over the next few days.

The Weather Takes Its Gloves Off--Strong Winds and Mountain Snow

2011-11-11T09:31:00.000-08:00

Missing Dog Update: My dog Leah was seen near the Moose Casino in Mountlake Terrace--66th Ave W and 220th St SW. If anyone is in the area and sees here, let us know right away! (see link on right)

We are now going into a very different, and much more active, weather period--and it starts today!

A strong front is now approaching the Washington coast and it will result in VERY strong winds in the Strait of Juan de Fuca, possible damage (power outages, localized flooding on Whidbey Island), blustery conditions and rain elsewhere, and snow in the mountains. And I don't even want to tell you what the models are suggesting for next weekend.

Perhaps the most profound weather phenomenon today is one I am actively researching: a powerful westerly wind surge in the Strait of Juan de Fuca.

Under the proper conditions, strong westerly winds can surge eastward into the Strait, reaching speeds of 50- 80 mph. Sometimes called Westerly Strait Surges, one will occur today. A particular strong surge destroyed Ivar's Mukilteo Landing restaurant in 2003 (now rebuilt and my favorite restaurant) and another heavily damaged the Washington Ferry Elwha when it was under repair in Everett Harbor (December 1990). Some pics of the damaged and rebuilt Ivars, which now has a weather theme:

The situation associated with westerly straight surges will occur today: a broad ridge over the eastern Pacific, northwesterly uper-level flow over western Washington, and a sharp trough pushing into our region in this flow. Here is the situation predicted for this afternoon at 500 hPa--about 18,000 ft above the surface:

You can see the strong trough embedded in intense northwesterly flow (remember the flow is parallel to the height lines and close spacing means strong winds). As the trough passes through the winds aloft are aligned with the Strait....here are the height lines at 850 hPa (around 5000 ft) to illustrate:

You see how the height lines, and thus winds, are parallel to the Strait? And the strong gradient of the height lines (thus strong winds) are clear. At the surface, the front is associated with a trough of low pressure, so as it passes eastward an intense low level pressure difference (high to the west, low to the east) develops and air likes to accelerate from high to low pressure. Here is the sea level pressure forecast for this afternoon at 4 PM. Pressure is increasing rapidly up the Strait.

Strong northwesterly winds aloft and big pressure difference down the Strait both support strong westerly winds that can slam in the eastern Strait, with Whidbey Island, Everett, and vicinity taking the brunt of it. Winds can gust to 40-80 mph. This one is not completely ideal....so I would not look beyond 60 mph today. Here are the WRF model forecasts for this afternoon at 1 PM. Strong sustained winds of 35 knots have pushed into the Strait (and gusts would be stronger).

Three hours later, strong winds have reached Whidbey Island and the eastern Strait (Port Townsend and the NE tip of the Olympic Peninsula should get a taste of this as well).

The freezing and snow levels should drop as cold air behind the front floods the region. With the flow directed up the mountains, enhanced precipitation in the form of snow should hit the mountains at and above pass level (more at the higher passes of course). Here is the forecast 24-h snowfall ending 4 AM on Saturday. The model suggests a foot in the northern Cascades dropping to an inch perhaps at Snoqualmie.

Then another system comes in on Saturday with more rain in the lowlands and snow in the Cascades. Here is the snowfall for the next 24-h--even more!

Good news for skiers!...we are going to start building the base they long for. Skiing by Thanksgiving may well be in sight.

And now let me tell you something that I shouldn't. The last few model cycles are suggesting a turn to colder temperatures on Thursday and the potential for lowland snow late Thursday or Friday. Too early to be sure at this point...so don't get too excited yet. I went to a meeting run by Seattle DOT this week on winter weather response...these folks are really girding up for battle. And this year they will have the new UW snow-weather application: SNOWWATCH...which I will describe this week.

Bering Superstorm

2011-11-08T22:20:00.000-08:00

An extraordinarily intense storm is now churning through the Bering Sea.

The central pressure is roughly 945 hPa--similar to a category three hurricane, and in fact this storm does have hurricane-force winds. (a hPa is the same as a millibar, mb, which you may be more familiar with. In the inches of mercury units this would be 27.9 inches). Take a look at a recent National Weather Surface surface analysis (for 4 PM Tuesday). 943 hPa low center and the NWS folks note the hurricane-force winds (sustained winds of 64 kt or more). That is a lot of isobars, with extraordinary pressure gradients.

It is quite unusual to have a storm this strong so far north. This storm developed very rapidly--approximately 60 hPa in 48 h, thus putting it in the category of explosive deepeners or "meteorological bombs" as known in the weather literature. Here is an image of the storm from of the polar orbiter weather satellites...the low center is in the middle of the swirl.

This storm is far deeper and stronger than the famous "Perfect Storm" of movie fame--at its most intense that low only got down to 972 hPa...nearly 30 hPa higher pressure. The has passed near a few weather buoys. Here are a few samples. Buoy 46070, found in the western Bering (see map) had a minimum pressure of 28.2 inches of Hg (954 hPa) and gust to nearly 60 kts.

Or Buoy 46035 (to the east) with gusts to 75 knots!

Wave heights at these locations climbed above 35 ft:

The fact that the storm is moving so quickly is preventing the waves from getting catastrophic since big waves requires strong winds, large fetch, and duration to build. Coastal flooding (up to 10 feet storm surge) and blizzard conditions add to the mix. In any case, this will be one of the great storms of the year.

Selected Peak Gusts from the NWS Hydrometeorological Prediction Center

.SELECTED PEAK WIND GUSTS IN MILES PER HOUR 

...ALASKA...
TIN CITY AFS (AWOS)                   85                     
WALES                                 84                     
CAPE LISBURNE(AWOS)                   75                     
KOTZEBUE/RALPH WIEN (ASOS)            73                     
KIVALINA ARPT                         71                     
POINT HOPE (AWOS)                     69                     
CAPE ROMANZOFF (AWOS)                 60                     
ST MICHAEL                            58                     
TELLER                                58                     
EMMONAK                               56                     
NOME (ASOS)                           55                     
BETHEL AIRPORT (ASOS)                 54                     
SAVOONGA AIRPORT                      54

Boring with a Hint of La Nina

2011-11-07T21:51:00.000-08:00

Sometimes the early part of November is the quiet before the storm; this has been true for the last few days and will continue for the remainder of the week. But don't forget: the last week of November on average brings the stormiest, wettest, meanest weather to the region. Meteorological ground zero for the Northwest. Turkey on the barbecue. And sometimes lowland snow--like November 22nd of last year.

Just to show you what I mean by boring, here is the National Weather Service forecast for this week:

Some clouds, some sun, a few light showers, temps reaching the 50s and dropping into the mid to lower 40s. Enough to drive a meteorologist mad.

But there are some interesting aspects of the atmospheric situation of the next few days, some indicative of our old friend-La Nina. Take a look at the 500 hPa upper level chart for Tuesday at 1 PM. A ridge over us (thus dry) and a high amplitude trough digging south from Alaska.

No umbrellas needed here. During the next few days an amazing thing happens. The trough deepens into a closed low off of California and becomes isolated from the jet stream to the north over the north Pacific and southern Canada. (remember the air flows parallel to the lines and is stronger where the lines are closer together).

There is a fancy name for this situation--a cut-off low: the low is cut-off from the jet stream. We are left in the dead zone...not much flow, not much action. And you will notice a BIG ridge (High) over the central Pacific--we will get back to that. Here is the precipitation over the West Coast for the next 72h. The action is pretty much all offshore.

But then things change a bit for Friday. The ridge builds offshore and the Northwest is in northwesterly flow (see below). A weak trough is embedded in this flow..which should bring some clouds and perhaps some light rain. Not too scary, but this pattern is reminiscent of a La Nina configuration, like last year when we were stuck in cold, northwesterly flow for months. If a trough develops with more amplitude and the ridge extends more into AK, we approach the canonical snow pattern.

On on Saturday...more of the same, but a bit stronger (see below). Expect a low snow level and decent snows in the mountain. The Mayor and SDOT don't have to worry...yet.

Don't forget to vote tomorrow...

The Great Raindrop Deception

2011-11-05T09:17:00.000-07:00

You have been deceived...by magazines, newspapers, the digital media, by artists, school teachers, and yes, even children's books. And it will stop here.

When raindrops are drawn, they almost always look the same way, as a teardrop. Some samples:

The problems is that raindrops virtually NEVER look like this! Northwesterns like us, with our persistent wet weather, should be expected to be fully educated in raindrop-ology, and thus this blog may serve as an important public service. Perhaps the Mayor will establish a raindrop education day this year.

Well, if raindrops never look like teardrops, what DO they look like? Well, it turns out that their shape depends on their size, a situation also obvious in humans. Small droplets are spherical, bigger ones like pancakes, and very large ones like parachutes. His is a graphical rendition:

Drizzle droplets (a Northwest favorite), with sizes of roughly .3 to .5 millimeter (mm), up to small raindrops, of approximately 1-1.5 mm, look pretty spherical. (For the metrically challenged... 1 mm is about .04 inches)

Why spherical? Surface tension--the attraction of water molecules to each other--pull the molecules together into a ball. Furthermore, small droplets don't weight that much and their fall velocity (also known as the terminal velocity) is relatively small, so the disturbing influence of the air moving around the droplets is minimal. I bet you have all noticed the difference in fall velocity of various size raindrops: drizzle drops seem to slowly drift down while big rains come down REAL fast.

For bigger droplets (2-3 mm), their weight causes them to fall faster, and the greater speed of the air passing around them causes them to be distorted into a pancake shape, with a nice little dimple in the middle.

For really big droplets, the distortion caused by the fast moving air is huge...the droplets get hollowed out into a parachute-like shape.

There is a limit to how big a raindrop can get because eventually the aerodynamics forces of the passing air tears it apart. What is the biggest raindrop ever observed? Well my University of Washington colleagues (Dr. Peter Hobbs and Art Rangno) may have seen the largest---8.8 mm (.35 inches!!)--in tropical cumulus. Imagine being hit by such a giant raindrops!

One final thing--our newly upgraded weather radars, with their fancy dual-polarization, have the capability to measure the shape of precipitation, including raindrops. Here is an example--the zdr product (stands for differential reflectivity). Zdr measures the difference in return between an up-down and side to side view of precipitation, thus giving information on the shape. When the returns in both directions are roughly the same (the difference between them being nearly zero), this product gives a value near zero. If the precipitation gets distorted, the number increases. Pretty neat stuff--measuring raindrop shape remotely. Looking at the image below, you can see a lot of near zero (blue) colors....not many teardrops here! The area of large values (white/gray colors) near Hoquiam is not meteorological--its ground clutter, where the radar beam is hitting the surface.

Zdr from the new NWS Langley Hill Doppler Radar

Finally, for those voters in Seattle, please keep in mind the Seattle School Board race and necessity to replace the current board members with those committed to better math education in our schools. The math textbooks used in Seattle are terrible at all levels and I see the impact on Seattle students coming to the UW--many of them have very weak math skills. We can do much better, this requires school board members that are willing to deal with the issue--the incumbents are not. The challengers (Peaslee, McLaren, Martin, Buetow) are all committed to dealing with the problem. The latest school board poll is here.

Mamma Mia! That's a Nice Front!

2011-11-02T22:02:00.000-07:00

Some nights are better than other for weather lovers, and tonight was a good one, with the strongest front of the fall moving through the region.

The new Langley Hill radar made it very clear that the approaching front was worth of some respect, with an extensive area of moderate and heavy rain. In the old days, we really would not have known this.

And we could savor the front as it made landfall and moved across the western lowlands.

Precipitation totals over the central and southern Sound were quite respectable, as shown the Seattle Rainwatch: .25-1 inch in many locations. Mayor McGinn introduced Rainwatch this week and it sent out warnings before the event.

Seattle Rainwatch 24-h totals ending around 9 PM Wed.

And the winds.... on the coast and over the eastern Strait, the winds gusted to 40-55 mph, while here in the lowlands, winds hit 30-35 mph, particularly over the water. Here is a plot of the wind gusts at Destruction Is, off the central WA coast---gust to 49 knots....56 mph. More than many folks saw for "Hurricane" Irene in NY and New England..

The strong, turbulent winds picked up the prodigiously falling leaves to create quite a spectacular scene in my neighborhood. Driving rain, gusting, roaring winds, a torrent of leaves--folks, it doesn't get better than this. And to frost the cake, during the next few hours light snow will fall in the mountains above roughly 3000 ft.

Northwest storm season has begun.

Finally, here is a marvelous video of today's show, starting with dense fog this morning that surges in and out, then clearing skies, followed by lowering cloud decks from the approaching front, and then heavy rain. Watch the speed of the clouds...the atmosphere goes into warp drive later in the day:

http://www.atmos.washington.edu/images/webcam0/movies/20111102.mov

If you are a Seattle resident and would like to participate in a poll on the Seattle School Board race, click here: http://www.easypolls.net/poll.html?p=4eb22007011eb0e4496235ab

Thursday Update: Snow in the Passes

No skiing....yet.

The Return of Mountain Snow and Some KUOW Comments

2011-11-01T13:29:00.000-07:00

October is now over and it was a very benign month, with temperatures and precipitation very close to normal. No big storms. A few weak fronts. Occasional sunny days and plenty of fog. And very little snow in the mountains.

But it looks like this is going to change, with the mountains beginning to build the wintertime base of snow that all skiers long for.

The first shot comes on Thursday, when a very deep trough moves over the West Coast, pushing the jet stream into California. Take a look at this 500 mb upper level chart at 2 PM on Thursday (below)...quite a deep trough over the northwest...and lots of rain and weather going into southern CA and the Southwest. Bad time in lotus land! And a huge ridge in the eastern Pacific....reminiscent of a La Nina-type pattern.

Here is the snowfall for the 24-h period ending 5 PM on Thursday--several inches in the Cascades--with some of it getting down to pass level (snow level descends to roughly 2500 ft). Not much, but a start.

Then another trough moves in on Saturday, and again the bulk of the flow going into California.

This relatively weak feature only provides a dusting of snow over the Cascades, perhaps and inch or two at the most.

But then on Monday another trough approaches--stronger and embedded in much stronger flow. This system could produce FAR heavier snowfall, with totals reaching a foot or more.

Of course, our confidence in the forecast declines in time, but it is clear that during the next week, a colder, wetter pattern more reminiscent of the La Nina situation of last year will set up. In fact, the NWS Climate Prediction Center forecasts for the next 6-10 days is for colder than normal and wetter than normal conditions (see graphics)---enough to warm the hearts of Northwest skiers hoping for an early start to the season. And yes...a reminder of last year.

KUOW Update

I have been fairly quiet about KUOW recently, not the least because I am really enjoying doing my weekly weather program on KPLU (Fridays at 9 AM) with Keith Seinfeld, their excellent science reporter. But all too often I get reminded about the attitudes over at KUOW, and particularly at Weekday, that I found so disturbing when I was on the inside. Case in point: Joel Connelly, the well-known PI reporter.   This week Joel wrote the following:

"Not long ago, on KUOW Radio -- before being exiled for protesting their ouster of weather expert Cliff Mass..."

Joel was one of the wisest and principled voices on the 10 AM "Week in Review" Friday program on KUOW, and a wonderful counterweight to the very conservative views of the Seattle Times' Joni Balter. He was a vocal critic of my "firing" for the terrible sin of talking about an education issue on one program--and wrote a very supportive piece in the PI on the subject. Turns out that criticism of Weekday staff or KUOW management is not allowed by this public radio station. It appears that by speaking his mind, Joel was given the boot....in a very similar way I was given the boot when I disagreed privately with Steve Scher's approach of selectively allowing certain opinions on his show. Folks--this is very disappointing behavior and quite frankly unacceptable for those responsible for a very important public radio outlet--a station whose license is held by the University of Washington.

And as long as I am complaining, why does KUOW Weekday insist on using a non-meteorologist, posing as a meteorologist, on many of their Friday shows?   This is about as reasonable as having a person without a medical degree doing surgery or providing detailed medical advice. And what does this say about journalistic integrity? The KUOW audience deserves better.

Local American Meteorological Society Meeting on Friday: Open to All

The Puget Sound Chapter of the American Meteorological Society will be meeting on Wednesday, November 2 at the Northeast Branch of the Seattle Public Library at 6:30 PM.   UW Graduate Student Luke Madaus will describe the new dual-polarization products available from the newly upgraded National Weather Service radars. All welcome.   Location: 6801 35th Ave. N.E. More directions at: http://www.spl.org/locations/northeast-branch/net-getting-to-the-branch

Nor'Easters versus Northwest Windstorms

2011-10-30T12:37:00.000-07:00

During the last day, a strong Nor'easter (also called Northeasters by some) struck the northeast U.S. with strong winds, rain in the coastal areas, and snow inland.

What made this storm so remarkable was the snow. Rarely do such storms bring this much snow so early. Usually the first snow of the season hits the coastal northeast U.S. in mid-December. From this events, some locations are breaking long term records--such as the earliest 1-inch snow for over a century at New York City. This storm is NOT a record for earliest snow over the region---historically, most northeast snow have had some snow as early as mid-October. Snow on trees that are still leafed is a major issue, resulting in lots of downed trees and power outages.

The weekend event is an example of a a Nor'easter--a strong, midlatitude cyclone (low pressure center) that moves up the east coast from the southwest to the northeast over the nearshore waters, roughly paralleling the coast. The winds move around such lows in a counterclockwise way, with the strongest winds generally from northeast over the north and western quadrants of the storm. Here is a National Weather Service surface chart at 10 PM PST on Saturday night as an example (solid lines are isobars--lines of constant pressure....the closer together they are, the generally the stronger the winds). Winds are shown by wind pennants at various stations.

Nor'easters are cousins to the big northwest windstorms (e.g., the Inauguration Day Windstorm, Chanukah Eve Windstorm, Columbus Day Storm). Both get most of their energy from horizontal variations in temperature--thus they are midlatitude cyclones. This is very different from tropical cyclones, such as hurricanes and typhoons, that derive their power from the warm temperatures and moisture of tropical oceans.

Both Northwest major cyclones and Nor'Easters have impressive satellite signatures, with characteristic cloud swirls and frontal cloud bands. Want to see? Here is an enhanced infrared image of the December 12, 1995 storm that hit us hard

and here is the latest east coast storm in the visible:

Large, impressive systems. For the Nor'eastern event...do you see that lines of clouds extending NW to SE from the coast---that is caused by cold air going over warm water.   In general, the very strongest Northwest cyclones are stronger than the top Nor'easters, with our 1962 Columbus Day storm probably being the most powerful non-tropical coastal storm to hit the U.S. in a century. (Beware--those wily east coasters like to call their storms "Perfect" or "Storm of the Century" and get books and movies made about them. Don't believe their propaganda--ours are bigger and more powerful).

Before roughly 1990, few of these big storms--on either coast--were well forecast by our numerical models. The 1962 Columbus Day storm came as a big surprise, and the President's Day Snowstorm of 1979 brought unforecast snow to D.C. (very bad place for forecast failures!).   But by the early 1990s something had changed. Our models now had sufficient resolution and physics, and satellite information was improving our description of the atmosphere to a point that we began to get these storms right.   For example, both the West Coast Inauguration Day Storm (January 1993) and the East Coast "Storm of the Century" (March 1993--I hate that name), were correctly predicted days before. And we have only gotten better in time.

Lets see how we did for the current storm.   Here is the model analysis at 5 PM on Saturday.

Nice low off the coast, large coast pressure variations. The dashed lines indicate lower atmosphere temperature, with the first blue one indication conditions cold enough for snow. The forecast by the National Weather Service GFS model initialized 36 hr before is shown below...as well as the precipitation forecast (light blue is the heaviest). Not bad!

Or how about 60hr before? Still quite good, but displaced a big too far offshore.

Keep in mind that some of these strong midlatitude cyclone can have hurricane force winds over water and are the equivalent of category 1-2 hurricanes. And midlatitude cyclones are much larger than tropical systems and do not weaken as quickly when they pass over land.

If a big midlatitude cyclone hits the Northwest this year we will have a magnificent view of the details using the new coastal radar. And if our models are wrong about intensity or position, the new radar will enable us to get out timely warnings in time to save property and lives. We have finally caught up to the east coast, where they have had radars looking offshore for decades.

Announcement: The Puget Sound Chapter of the American Meteorological Society will be meeting on Wednesday, November 2 at the Northeast Branch of the Seattle Public Library at 6:30 PM. UW Graduate Student Luke Madaus will describe the new dual-polarization products available from the newly upgraded National Weather Service radars. All welcome. Location: 6801 35th Ave. N.E. More directions at: http://www.spl.org/locations/northeast-branch/net-getting-to-the-branch